[Question]
  [
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[Improve this question](/posts/20914/edit) 
Objective:
> 
> The task is to create a chatbot with whom you can spend your time discussing your deepest thoughts with. Create a chatbot with an AI that learns from your input. Your bot should inspire you to releave your darkest inner truths.
> 
> 
> 
Inspiration:
> 
> <http://en.wikipedia.org/wiki/Chatterbot>
> 
> 
> <http://io9.com/5901579/10-tricks-that-chatbots-use-to-make-you-believe-theyre-human>
> 
> 
> 
**Rules:**
1. You can use any programming language.
2. Your programs should not take any input from filename, network or anything else but the user input.
3. There can be no preset vocabulary, the bot should learn everything it knows from the user input, and the discussion can be about anything.
**Mandatory criterias:**
1. This is not Code-golf, but please keep it simple, sourcecode size should correspond to programming language, meaning: GolfScript=short, BF=long, other=Use common sense. Use the example code as a reference, your code may be double that size, but then it better be good.
2. Your program can not start to lag (5-10 seconds delay) within the first 1000 sentences.
3. A reasonable discussion should take form within about 20-30 sentences.
4. Your algorithm should differ, in logic, from the example code as much as it can.
**Optional bonus judging criterias:**
1. The better bot learning algorithm, the better program.
2. No tennis match, i.e conversation does not follow the strict: “user > computer > user”-loop turns.
3. Less mimic, bot behaviour is different from user behaviour, separating the perception of the bot attitude from the user attitude.
4. Sense different changing moods, for example: talkative, taciturn, optimistic, pessimistic.
5. A way of saving and loading the "brain", so that you can continue your discussion with your bot another day.
**Example code in c++ for inspiration only:**
```
#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <iterator>
using namespace std;
vector<string> words;
vector<int> weight1;
vector<int> weight2;
int oldbw;
int collect(string const& i, int w1, int w2) 
{
    istringstream iss(i), iss2(i);
    copy(istream_iterator<string>(iss),
             istream_iterator<string>(),
             back_inserter(words));
    words.insert(words.end(), "\n");
    int a = distance(istream_iterator<string>(iss2), istream_iterator<string>());
    for(int c=0;c<=a;c++) weight1.insert(weight1.end(), w1);
    for(int c=0;c<=a;c++) weight2.insert(weight2.end(), w2);
    return a;
}
void answer(int c) 
{
    string op;
    int bs=0,bw=0,cs,si,searchsize,cc, c2;
    cout << "BRAIN: ";
    for(int iwrd = words.size()-c; iwrd >= 0; iwrd--)
    {
        searchsize = words.size()/4;
        cs = 0; si=searchsize;
        for(int iw = words.size()-2; (iw >= 0 && si!=0); iw--) 
        {   
            cc = iwrd-searchsize+si;
            if (cc>=0) if (words[cc]!="\n" && words[cc]==words[iw]) cs += si*(weight2[cc]-weight1[cc]);
            si--;
        }
        if(cs>=bs && iwrd<(int)words.size()*0.9 && abs(iwrd-oldbw)>((int)words.size()/5)) 
        {bs=cs; bw = iwrd;}
    }
    oldbw=bw;
    if(bw<0)bw=0;
    for(c2=bw; c2< (int)words.size()-1;c2++) if(words[c2]=="\n") {bw=c2+1;break;}
    
    for(c2=0;(bw+c2) < (int)words.size();c2++)
        if(words[bw+c2]!="\n") op += words[bw+c2] + " "; else break;
    c2=0;
    while(c>=0) 
    {
        if(bw-(++c2)>=0)
        {
            if(weight1[bw-c2]>0) { weight1[bw-c2]--; c--; }
        } else c=-1;
        if(bw+c2>=0)
        {
            if(weight2[bw+c2]>0) { weight2[bw+c2]--; c--; }
        } else c=-1;
    }
    collect(op,3,5);    
    cout << op << "\n  YOU: ";
}
int main() {
    string i;
    oldbw=0;
    do { getline(cin, i); answer(collect(i,5,3)+1);} while(i.compare("exit")!=0);
    return 0;
}
```
**Sample dialog:**
```
Hello there, crazy bot!
BRAIN: Hello there, crazy bot!
  YOU: I am not a crazy bot, I am pure human (and some cheese).
BRAIN: I am not a crazy bot, I am pure human (and some cheese).
  YOU: What cheese are you?
BRAIN: I am not a crazy bot, I am pure human (and some cheese).
  YOU: You did tell me that already.
BRAIN: You did tell me that already.
  YOU: I did not, stop bugging me, you crazy bot!
BRAIN: I am not a crazy bot, I am pure human (and some cheese).
  YOU: Are you a human? How come?
BRAIN: You did tell me that already.
  YOU: I will hunt you down the longests roads
BRAIN: What cheese are you?
  YOU: I am a pink cheese, with some butter. That makes sense to me.
BRAIN: You did tell me that already.
  YOU: Stop telling me that, who are you?
BRAIN: What cheese are you?
  YOU: I tell you what cheese I am if you tell me your name!
BRAIN: What cheese are you?
  YOU: Oh my god! This is leading towards nowhere.
BRAIN: What cheese are you?
  YOU: Oh no, my head hurts. Are you a crazy bot or not?
BRAIN: Are you a human? How come?
  YOU: That is enough! Can we talk about something more funny?
BRAIN: Oh no, my head hurts. Are you a crazy bot or not?
  YOU: I am HUMAN!
BRAIN: What cheese are you?
  YOU:
```
This is a popularity-contest, the answer with the most upvotes by 2014-04-01 wins!
**Good luck, have fun!**
  
[Answer]
# Java
**New Edit**: Still more tweaking in spare time. I've started a new branch, where I've been playing with the DFS algorithm. Officially the branch is to act as core to a new BFS algorithm I'm planning, but in the meantime I wanted to get a better handle on what the DFS is doing, and how it's making its decisions. To that end, I've added a suppression function that begins to decay the value of a new word, regardless of topic-ness or not, as sentences grow longer. As well, all words contribute value to the sentence now, but words that aren't in the topic or sentence topic list contribute just 25% of their frequency value. An example conversation [can be found here](https://github.com/ProgrammerDan/learning-chatbot/blob/bfs/ExampleConversation3.md) and it's quite good, where we talk about physics, the human nature of Chatbrains, and other fascinating topics. Check out the [branch code here](https://github.com/ProgrammerDan/learning-chatbot/blob/bfs/LearningChatbot.java).
**Edit**: I've been tweaking the code a bit. Instead of posting the revisions here, check it out [at my github repository](https://github.com/ProgrammerDan/learning-chatbot) where you will find the latest revisions. I've also added a new conversation against the most recent version, where we discuss chatbots, depth first search, and how programming should be used to build living things!.
I decided to embrace this challenge holistically. My chatbot knows very few things starting out -- no words, no syntax, no nothing. It knows how to parse standard English into words, and how to identify non-word characters as punctuation. That's it. Everything it knows it learns from interaction with the user. As you interact with it, it pays attention to the connections between words, and constructs sentences using that information. Of course, reference the source for more information. I've greatly exceeded the recommended length-of-program expectations of this challenge, but to a good purpose. Here are some highlights of the program:
* Chatbot starts with no knowledge (follows **"Rules":3**)
* Frequency of word occurrence is tracked
* Word frequencies are "decayed" so that conversation can move from topic to topic (follows **"Bonus":3 and 4**)
* The arrangement of words in observed sentences is recorded, so "phrases" are implicitly kept track of (e.g. if you use a lot of prepositional phrases when chatting with the bot, the bot will use a lot of them too!)
* Sentences are built by preferring to follow most frequently observed connections between words, with random factors to inject variation
* The sentence construction algorithm is a Depth First Search, that attempts to maximize occurrence of topic words in the output sentence, with a small preference for ending sentences (this follows **"Bonus":1** -- I use a pretty damn cool learning algorithm, that shifts over time and retains knowledge of harvested word connections)
	+ *edit:* Topic words are now drawn from both global knowledge of reoccurring words, and from the most recent sentence
	+ *edit:* Words weights are now computed using log base 4 of the word length, so longer words are weighted more strongly, and shorter words, more weakly -- this is to make up for the lack of a true corpus to use in both weighting and eliminating high-frequency, low value words as one can easily do with a corpus.
	+ *edit:* As the sentence length grows during construction, a suppression function begins to decrease the value of additional words.
	+ *edit:* Sentence "ending" is less valuable now, as it was causing a preponderance of short silly sentences.
	+ *edit:* All words now contribute value, although off-topic words only contribute at 25% of global frequency value.
	+ There is a built-in depth maximum to prevent too much looping and too much time spent because of my use of word precedent to build a sentence
	+ Loops are detected directly while building a sentence, and while they are technically allowed, there is a high chance that loops will be avoided
	+ Tune-able timeout is used to encourage both branch pruning and statement finalization, and also to prevent going past the 5-10 second "acceptable delay" in the rules
To summarize my connection to the rules:
* For **"Rules":1**, I chose Java, which is verbose, so be gentle.
* For **"Rules":2**, user input alone is leveraged, although I have some stub code to add brain saving/loading for the future
* For **"Rules":3**, there is absolutely no pre-set vocabulary. The ChatBot knows how to parse English, but that's it. Starting out, it knows absolutely nothing.
* For **"Mandatory Criteria":1**, my program is longer, but packs a lot of awesome. I hope you'll overlook.
* For **"Mandatory Criteria":2**, I have a timeout on my sentence construction algorithm to explicitly prevent more than 5-6 seconds search time. The best sentence so far is returned on timeout.
* For **"Mandatory Criteria":3**, Topics generally solidify in about 10 sentences, so the Bot will be on-topic by then, and by 20 sentences will be responding to statements with some fascinating random constructs that actually make a bit of sense.
* For **"Mandatory Criteria":4**, I borrowed nothing from the reference code. This is an entirely unique construction.
* For **"Bonus":1**, I like to think this bot is quite exceptional. It won't be as convincing as scripted bots, but it has absolutely no limitations on topics, and will move gracefully (with persistence) from conversation topic to topic.
* For **"Bonus":2**, this is strictly round-robin, so no bonus here. Yet. There's no requirement within my algorithm for response, so I'm planning a Threaded version that will address this bonus.
* For **"Bonus":3**, initially this bot will mimic, but as the conversation progresses beyond the first few sentences, mimicing will clearly end.
* For **"Bonus":4**, "moods" aren't processed in any meaningful way, but as the bot preferences topic following, it will shift moods.
* For **"Bonus":5**, saving and loading brain is not currently in place.
So, I've met all base rules, all mandatory rules, and provisionally bonus rules 1, 3, and 4.
As another bonus, I've commented all throughout the code, so feel free to borrow or make recommendations for improvements. Clearly, as I have no built-in dialogue and no "structural" knowledge, conversations will be weird for longer then other bots, but I think I meet the rules pretty well.
Now, on to the code (Some comments redacted to fit body limit) [or follow it on GitHub, as I continue to improve it](https://github.com/ProgrammerDan/learning-chatbot/blob/bfs/LearningChatbot.java):
```
import java.util.*;
import java.util.regex.*;
public class LearningChatbot {
    /**
     * Static definition of final word in a statement. It never has 
     * any descendents, and concludes all statements. This is the only
     * "starting knowledge" granted the bot.
     */
    public static final ChatWord ENDWORD = new ChatWord("\n");
    /**
     * The Brain of this operation.
     */
    private ChatbotBrain brain;
    /**
     * Starts LearningChatbot with a new brain
     */
    public LearningChatbot() {
        brain = new ChatbotBrain();
    }
    /**
     * Starts LearningChatbot with restored brain.
     */
    public LearningChatbot(String filename) {
        throw new UnsupportedOperationException("Not yet implemented");
    }
    /**
     * Invocation method.
     */
    public void beginConversation() {
        ChatbotBrain cb = new ChatbotBrain();
        Scanner dialog = new Scanner(System.in);
        boolean more = true;
        while (more) {
            System.out.print("    You? ");
            String input = dialog.nextLine();
            if (input.equals("++done")) {
                System.exit(0);
            } else if (input.equals("++save")) {
                System.out.println("Saving not yet implemented, sorry!");
                System.exit(0);
            } else if (input.equals("++help")) {
                getHelp();
            }else {
                cb.decay();
                cb.digestSentence(input);
            }
            System.out.print("Chatbot? ");
            System.out.println(cb.buildSentence());
        }
    }
    /**
     * Help display
     */
    public static void getHelp() {
        System.out.println("At any time during the conversation, type");
        System.out.println("   ++done");
        System.out.println("to exit without saving.");
        System.out.println("Or type");
        System.out.println("   ++save");
        System.out.println("to exit and save the brain.");
        System.out.println();
    }
    /**
     * Get things started.
     */
    public static void main(String[] args) {
        System.out.println("Welcome to the Learning Chatbot");
        System.out.println();
        getHelp();
        LearningChatbot lc = null;
        if (args.length > 0) {
            System.out.printf("Using %s as brain file, if possible.", args[0]);
            lc = new LearningChatbot(args[0]);
        } else {
            lc = new LearningChatbot();
        }
        lc.beginConversation();
    }
    /**
     * The ChatbotBrain holds references to all ChatWords and has various
     * methods to decompose and reconstruct sentences.
     */
    static class ChatbotBrain {
        /**
         * A tracking of all observed words. Keyed by the String version of
         * the ChatWord, to allow uniqueness across all ChatWords
         */
        private Map<String,ChatWord> observedWords;
        /**
         * This brain is going to be able to keep track of "topics" by way of
         * a word frequency map. That way, it can generate sentences based
         * on topic-appropriateness.
         */
        private Map<ChatWord, Double> wordFrequencyLookup;
        /**
         * This holds the actual word frequencies, for quick isolation of
         * highest frequency words.
         */
        private NavigableMap<Double, Collection<ChatWord>> wordFrequency;
        /**
         * This holds the count of words observed total.
         */
        private int wordCount;
        /**
         * This holds the current "values" of all words.
         */
        private double wordValues;
        /**
         * A "word" that is arbitrarily the start of every sentence
         */
        private ChatWord startWord;
        /**
         * Rate of decay of "topics".
         */
        private double decayRate;
        // These values configure various features of the recursive 
        // sentence construction algorithm.
        /** Nominal (target) length of sentences */
        public static final int NOMINAL_LENGTH = 10;
        /** Max length of sentences */
        public static final int MAX_LENGTH = 25;
        /** Sentence creation timeout */
        public static final long TIMEOUT = 5000;
        /** Topic words to match against */
        public static final int TOPICS = 3;
        /** Minimum branches to consider for each word */
        public static final int MIN_BRANCHES = 3;
        /** Maximum branches to consider for each word */
        public static final int MAX_BRANCHES = 5;
        /** % chance as integer out of 100 to skip a word */
        public static final int SKIP_CHANCE = 20;
        /** % chance as integer to skip a word that would cause a loop */
        public static final int LOOP_CHANCE = 5;
        /** % chance that punctuation will happen at all */
        public static final int PUNCTUATION_CHANCE = 25;
        /** % chance that a particular punctuation will be skipped */
        public static final int PUNCTUATION_SKIP_CHANCE = 40;
        /**
         * Convenience parameter to use a common random source 
         * throughout the brain.
         */
        private Random random;
        /**
         * Gets the Chatbot started, sets up data structures necessary
         */
        public ChatbotBrain() {
            observedWords = new HashMap<String,ChatWord>();
            observedWords.put("\n",ENDWORD);
            startWord = new ChatWord("");
            observedWords.put("",startWord);
            wordFrequencyLookup = new HashMap<ChatWord, Double>();
            wordFrequency = new TreeMap<Double, Collection<ChatWord>>();
            decayRate = 0.05;
            wordCount = 0;
            wordValues = 0.0;
            random = new Random();
        }
        /**
         * More complex digest method (second edition) that takes a sentence,
         * cuts it pu, and links up the words based on ordering.
         */
        public void digestSentence(String sentence) {
            Scanner scan = new Scanner(sentence);
            ChatWord prior = null;
            ChatWord current = null;
            String currentStr = null;
            String currentPnc = null;
            while (scan.hasNext()) {
                currentStr = scan.next();
                Pattern wordAndPunctuation = 
                        Pattern.compile("([a-zA-Z\\-_'0-9]+)([^a-zA-Z\\-_'0-9]?)[^a-zA-Z\\-_'0-9]*?");
                Matcher findWords = wordAndPunctuation.matcher(currentStr);
                //  Basically this lets us find words-in-word typos like this:
                //  So,bob left his clothes with me again.
                //  where "So,bob" becomes "So," "bob"
                while (findWords.find()) {
                    currentStr = findWords.group(1);
                    currentPnc = findWords.group(2);
                    if (currentStr != null) {
                        if (observedWords.containsKey(currentStr)) {
                            current = observedWords.get(currentStr);
                        } else {
                            current = new ChatWord(currentStr);
                            observedWords.put(currentStr, current);
                        }
                        incrementWord(current);
                        if (currentPnc != null && !currentPnc.equals("")) {
                            current.addPunctuation(currentPnc.charAt(0));
                        }
                        if (prior != null) {
                            prior.addDescendent(current);
                        }
                        if (prior == null) {
                            startWord.addDescendent(current);
                        }
                        prior = current;
                    }
                }
            }
            if (prior != null) { // finalize.
                prior.addDescendent(ENDWORD);
            }
        }
        /**
         * Increments the value of a word (catalogues a new sighting).
         */
        public void incrementWord(ChatWord word) {
            Double curValue;
            Double nextValue;
            Collection<ChatWord> freqMap;
            if (wordFrequencyLookup.containsKey(word)) {
                curValue = wordFrequencyLookup.get(word);
                freqMap = wordFrequency.get(curValue);
                freqMap.remove(word);
            } else {
                curValue = 0.0;
            }
            nextValue=curValue+1.0;
            wordFrequencyLookup.put(word, nextValue);
            freqMap = wordFrequency.get(nextValue);
            if (freqMap == null) {
                freqMap = new HashSet<ChatWord>();
                wordFrequency.put(nextValue, freqMap);
            }
            freqMap.add(word);
            wordCount++;
            wordValues++;
        }
        /**
         * Decays a particular word by decay rate.
         */
        public void decayWord(ChatWord word) {
            Double curValue;
            Double nextValue;
            Collection<ChatWord> freqMap;
            if (wordFrequencyLookup.containsKey(word)) {
                curValue = wordFrequencyLookup.get(word);
                freqMap = wordFrequency.get(curValue);
                freqMap.remove(word);
            } else {
                return;
            }
            wordValues-=curValue; // remove old decay value
            nextValue=curValue-(curValue*decayRate);
            wordValues+=nextValue; // add new decay value
            wordFrequencyLookup.put(word, nextValue);
            freqMap = wordFrequency.get(nextValue);
            if (freqMap == null) {
                freqMap = new HashSet<ChatWord>();
                wordFrequency.put(nextValue, freqMap);
            }
            freqMap.add(word);
        }
        /**
         * Decay all word's frequency values. 
         */
        public void decay() {
            for (ChatWord cw : wordFrequencyLookup.keySet()) {
                decayWord(cw);
            }
        }
        /**
         * Gets a set of words that appear to be "top" of the frequency
         * list.
         */
        public Set<ChatWord> topicWords(int maxTopics) {
            Set<ChatWord> topics = new HashSet<ChatWord>();
            int nTopics = 0;
            for (Double weight: wordFrequency.descendingKeySet()) {
                for (ChatWord word: wordFrequency.get(weight)) {
                    topics.add(word);
                    nTopics++;
                    if (nTopics == maxTopics) {
                        return topics;
                    }
                }
            }
            return topics;
        }
        /**
         * Uses word frequency records to prefer to build on-topic
         * sentences.
         */
        public String buildSentence() {
            int maxDepth = NOMINAL_LENGTH+
                    random.nextInt(MAX_LENGTH - NOMINAL_LENGTH);
            ChatSentence cs = new ChatSentence(startWord);
            // We don't want to take too long to "think of an answer"
            long timeout = System.currentTimeMillis() + TIMEOUT;
            double bestValue = buildSentence(cs, topicWords(TOPICS), 0.0, 0, maxDepth, timeout);
            return cs.toString();
        }
        public double buildSentence(ChatSentence sentence, 
                Set<ChatWord> topics, double curValue,
                int curDepth, int maxDepth, long timeout){
            if (curDepth==maxDepth || System.currentTimeMillis() > timeout) {
                return curValue;
            }
            // Determine how many branches to enter from this node
            int maxBranches = MIN_BRANCHES + random.nextInt(MAX_BRANCHES - MIN_BRANCHES);
            // try a few "best" words from ChatWord's descendent list.
            ChatWord word = sentence.getLastWord();
            NavigableMap<Integer, Collection<ChatWord>> roots =
                    word.getDescendents();
            // Going to keep track of current best encountered sentence
            double bestSentenceValue = curValue;
            ChatSentence bestSentence = null;
            int curBranches = 0;
            for (Integer freq : roots.descendingKeySet()) {
                for (ChatWord curWord : roots.get(freq)) {
                    if (curWord.equals(ENDWORD)) {
                        // let's weigh the endword cleverly
                        double endValue = random.nextDouble() * wordFrequency.lastKey();
                        if (curValue+endValue > bestSentenceValue) {
                            bestSentenceValue = curValue+endValue;
                            bestSentence = new ChatSentence(sentence);
                            bestSentence.addWord(curWord);
                        }
                        curBranches++;
                    } else {
                        int chance = random.nextInt(100);
                        boolean loop = sentence.hasWord(curWord);
                        /* Include a little bit of chance in the inclusion of
                         * any given word, whether a loop or not.*/
                        if ( (!loop&&chance>=SKIP_CHANCE) ||
                                (loop&&chance<LOOP_CHANCE)) {
                            double wordValue = topics.contains(curWord)?
                                    wordFrequencyLookup.get(curWord):0.0;
                            ChatSentence branchSentence = new ChatSentence(sentence);
                            branchSentence.addWord(curWord);
                            addPunctuation(branchSentence);
                            double branchValue = buildSentence(branchSentence,
                                    topics, curValue+wordValue, curDepth+1,
                                    maxDepth, timeout);
                            if (branchValue > bestSentenceValue) {
                                bestSentenceValue = branchValue;
                                bestSentence = branchSentence;
                            }
                            curBranches++;
                        }
                    }
                    if (curBranches == maxBranches) break;
                }
                if (curBranches == maxBranches) break;
            }
            if (bestSentence != null) {
                sentence.replaceSentence(bestSentence);
            }
            return bestSentenceValue;
        }
        /**
         * Adds punctuation to a sentence, potentially.
         */
        public void addPunctuation(ChatSentence sentence) {
            ChatWord word = sentence.getLastWord();
            NavigableMap<Integer, Collection<Character>> punc = word.getPunctuation();
            if (punc.size()>0 && random.nextInt(100)<PUNCTUATION_CHANCE){
                Integer puncMax = punc.lastKey();
                Collection<Character> bestPunc = punc.get(puncMax);
                Character puncPick = null;
                for (Integer freq : punc.descendingKeySet()) {
                    for (Character curPunc : punc.get(freq)) {
                            if (random.nextInt(100)>=PUNCTUATION_SKIP_CHANCE) {
                                puncPick = curPunc;
                                break;
                            }
                    }
                    if (puncPick != null) break;
                }
                if (puncPick != null) {
                    sentence.addCharacter(puncPick);
                }
            }
        }
        @Override
        public String toString() {
            StringBuilder sb = new StringBuilder();
            sb.append("ChatBrain[");
            sb.append(observedWords.size());
            sb.append("]:");
            for (Map.Entry<String,ChatWord> cw : observedWords.entrySet()) {
                sb.append("\n\t");
                sb.append(wordFrequencyLookup.get(cw.getValue()));
                sb.append("\t");
                sb.append(cw.getValue());
            }
            return sb.toString();
        }
    }
    /**
     * Useful helper class to construct sentences.
     */
    static class ChatSentence implements Cloneable {
        /**
         * List of words.
         */
        private List<Object> words;
        /**
         * Quick search construct to have O(ln) lookup times.
         */
        private Set<Object> contains;
        /**
         * Starts to build a sentence with a single word as anchor
         */
        public ChatSentence(ChatWord anchor) {
            if (anchor == null) {
                throw new IllegalArgumentException("Anchor must not be null");
            }
            words = new ArrayList<Object>();
            contains = new HashSet<Object>();
            words.add(anchor);
            contains.add(anchor);
        }
        /** 
         * Starts a sentence using an existing ChatSentence. Also used for
         * cloning.
         */
        public ChatSentence(ChatSentence src) {
            words = new ArrayList<Object>();
            contains = new HashSet<Object>();
            appendSentence(src);
        }
        /**
         * Adds a word to a sentence
         */
        public ChatSentence addWord(ChatWord word) {
            if (word == null) {
                throw new IllegalArgumentException("Can't add null word");
            }
            words.add(word);
            contains.add(word);
            return this;
        }
        /**
         * Adds a character to a sentence.
         */
        public ChatSentence addCharacter(Character punc) {
            if (punc == null) {
                throw new IllegalArgumentException("Can't add null punctuation");
            }
            words.add(punc);
            contains.add(punc);
            return this;
        }
        /**
         * Replace a sentence with some other sentence.
         * Useful to preserve references.
         */
        public ChatSentence replaceSentence(ChatSentence src) {
            words.clear();
            contains.clear();
            appendSentence(src);
            return this;
        }
        public ChatSentence appendSentence(ChatSentence src) {
            words.addAll(src.getWords());
            contains.addAll(src.getWords());
            return this;
        }
        /**
         * Get last word of the sentence.
         */
        public ChatWord getLastWord() {
            for (int i=words.size()-1; i>=0; i--) {
                if (words.get(i) instanceof ChatWord) {
                    return (ChatWord) words.get(i);
                }
            }
            throw new IllegalStateException("No ChatWords found!");
        }
        /**
         * Checks if the sentence has a word
         */
        public boolean hasWord(ChatWord word) {
            return contains.contains(word);
        }
        /**
         * Counts the number of words in a sentence.
         */
        public int countWords() {
            int cnt = 0;
            for (Object o : words) {
                if (o instanceof ChatWord) {
                    cnt++;
                }
            }
            return cnt;
        }
        /**
         * Gets all the words of the sentence
         */
        private List<Object> getWords() {
            return words;
        }
        /**
         * Returns the sentence as a string.
         */
        @Override
        public String toString() {
            StringBuffer sb = new StringBuffer();
            for (Object o : words) {
                if (o instanceof ChatWord) {
                    ChatWord cw = (ChatWord) o;
                    sb.append(" ");
                    sb.append( cw.getWord() );
                } else {
                    sb.append(o);
                }
            }
            return sb.toString().trim();
        }
        /**
         * Clones this sentence.
         */
        @Override
        public Object clone() {
            return new ChatSentence(this);
        }
    }
    /**
     * ChatWord allows the creation of words that track how they are
     * connected to other words in a forward fashion. 
     */
    static class ChatWord {
        /** The word. */
        private String word;
        /** Collection of punctuation observed after this word */
        private NavigableMap<Integer, Collection<Character>> punctuation;
        /** Lookup linking observed punctuation to where they are in ordering */
        private Map<Character, Integer> punctuationLookup;
        /** Punctionation observation count */
        private Integer punctuationCount;
        /** Collection of ChatWords observed after this word */
        private NavigableMap<Integer, Collection<ChatWord>> firstOrder;
        /** Lookup linking observed words to where they are in ordering */
        private Map<ChatWord, Integer> firstOrderLookup;
        /** First order antecedent word count */
        private Integer firstOrderCount;
        /**
         * Creates a new ChatWord that is aware of punctuation that
         * follows it, and also ChatWords that follow it.
         */
        public ChatWord(String word){
            this.word = word;
            this.firstOrder = new TreeMap<Integer, Collection<ChatWord>>();
            this.firstOrderLookup = new HashMap<ChatWord, Integer>();
            this.firstOrderCount = 0;
            this.punctuation = new TreeMap<Integer, Collection<Character>>();
            this.punctuationLookup = new HashMap<Character, Integer>();
            this.punctuationCount = 0;
        }
        protected NavigableMap<Integer, Collection<ChatWord>> getDescendents() {
            return firstOrder;
        }
        /**
         * Returns how many descendents this word has seen.
         */
        protected int getDescendentCount() {
            return firstOrderCount;
        }
        /**
         * Gets the lookup map for descendents
         */
        protected Map<ChatWord, Integer> getDescendentsLookup() {
            return firstOrderLookup;
        }
        /** As conversation progresses, word orderings will be encountered.
         * The descendent style of "learning" basically weights how often
         * words are encountered together, and is strongly biased towards
         * encountered ordering.
         */
        public void addDescendent(ChatWord next) {
            if(next != null){
                firstOrderCount++;
                int nextCount = 1;
                Collection<ChatWord> obs = null;
                // If we've already seen this word, clean up prior membership.
                if(firstOrderLookup.containsKey(next)){
                    nextCount = firstOrderLookup.remove(next);
                    obs = firstOrder.get(nextCount);
                    // Remove from prior obs count order
                    obs.remove(next);
                    nextCount++;
                }
                obs = firstOrder.get(nextCount);
                if (obs == null) { // we don't have this order yet
                    obs = new HashSet<ChatWord>();
                    firstOrder.put(nextCount, obs);
                }
                firstOrderLookup.put(next, nextCount);
                obs.add(next);
            }
        }
        /**
         * Some words have punctuation after them more often than not. 
         * This allows the ChatBrain to record occurrences of punctuation
         * after a word.
         */
        public void addPunctuation(Character punc) {
            if(punc != null){
                punctuationCount++;
                int puncCount = 1;
                Collection<Character> obs = null;
                // If we've already seen this punc, clean up prior membership.
                if(punctuationLookup.containsKey(punc)){
                    puncCount = punctuationLookup.remove(punc);
                    obs = punctuation.get(puncCount);
                    // Remove from prior obs count order
                    obs.remove(punc);
                    puncCount++;
                }
                obs = punctuation.get(puncCount);
                if (obs == null) { // we don't have this order yet
                    obs = new HashSet<Character>();
                    punctuation.put(puncCount, obs);
                }
                punctuationLookup.put(punc, puncCount);
                obs.add(punc);
            }
        }
        /**
         * Including this for now, but I don't like it -- it returns all
         * punctuation wholesale. I think what would be better is some
         * function that returns punctuation based on some characteristic.
         */
        protected NavigableMap<Integer, Collection<Character>> getPunctuation() {
            return punctuation;
        }
        /**
         * Gets count of punctuation encountered.
         */
        protected int getPunctuationCount() {
            return punctuationCount;
        }
        /**
         * Gets lookup of punctuations encountered.
         */
        protected Map<Character, Integer> getPunctuationLookup() {
            return punctuationLookup;
        }
        /**
         * Gets the String backing this ChatWord.
         */
        public String getWord() {
            return word;
        }
        /**
         * ChatWords are equivalent with the String they wrap.
         */
        @Override
        public int hashCode() {
            return word.hashCode();
        }
        /**
         * ChatWord equality is that ChatWords that wrap the same String
         * are equal, and a ChatWord is equal to the String that it contains.
         */
        @Override
        public boolean equals(Object o){
            if (o == this) {
                return true;
            }
            if (o instanceof ChatWord) {
                return ((ChatWord)o).getWord().equals(this.getWord());
            }
            if (o instanceof String) {
                return ((String)o).equals(this.getWord());
            }
            return false;
        }
        /**
         * Returns this ChatWord as a String.
         */
        @Override
        public String toString() {
            StringBuilder sb = new StringBuilder();
            sb.append("ChatWord[");
            sb.append(word);
            sb.append("]desc{");
            for (Integer key : firstOrder.keySet() ) {
                Collection<ChatWord> value = firstOrder.get(key);
                sb.append(key);
                sb.append(":[");
                for (ChatWord cw : value) {
                    sb.append(cw.getWord());
                    sb.append(",");
                }
                sb.append("],");
            }
            sb.append("}punc{");
            for (Integer key : punctuation.keySet() ) {
                Collection<Character> value = punctuation.get(key);
                sb.append(key);
                sb.append(":[");
                for (Character c : value) {
                    sb.append("\"");
                    sb.append(c);
                    sb.append("\",");
                }
                sb.append("],");
            }
            sb.append("}");
            return sb.toString();
        }
    }
}
```
Sample conversation:
[Linked b/c of post character limits](https://github.com/ProgrammerDan/learning-chatbot/blob/master/ExampleConversation.md)
[Conversation where the Bot tells me I should program living things](https://github.com/ProgrammerDan/learning-chatbot/blob/master/ExampleConversation2.md)
[Latest conversation where the Bot talks about the true nature of Chatbrains, physics, the physical universe, and how I am most likely also a Chatbrain](https://github.com/ProgrammerDan/learning-chatbot/blob/bfs/ExampleConversation3.md)
and so on. I have a few things I'm going to add -- for instance, because of the commonality of simple words, they tend to dominate uncurated topic lists. I'm going to add in a percentage skip to topic words so that common words are skipped.
[Answer]
# C++
Now I just need to write the algorithm for carrying on a conversation. My first machine-learning exercise.
```
#include <iostream>
#include <string>
#include <vector>
#include <ctime>
#include <fstream>
using namespace std;
int randint(int n) {return rand()%n;}
bool old_response(string r, vector<string>v){
  for(int i = 0; i < v.size(); i++) if(r == v[i]) return true;
  return false;
}
void output(vector<string>v) {cout<< "CHATBOT:\t" << v[randint(v.size())] << endl;}
void delay(int sum_response, int sum_time) {
  if(sum_response != 0) {
    int t = time(0);
    while(true)if(time(0) == t+sum_time/sum_response)break;
  }
}
int main() {
  string name = "";
  cout<<"Please enter your name: ";
  getline(cin, name);
  vector<string> responses;
  ifstream ifs("responses.txt");
  if(ifs) {
    do {
      string s = "";
      getline(ifs, s);
      if(ifs.eof()) break;
      responses.push_back(s);
    } while(!ifs.eof());
  }
  string response = "";
  getline(cin, response);
  int time1 = time(0);
  int sum_time = 0;
  int sum_response = 0;
  do {
    if(!old_response(response, responses)) responses.push_back(response);
    delay(sum_response, sum_time);
    output(responses);
    
    cout << name << ":\t";
    getline(cin, response);
    sum_time += time(0)-time1;
    sum_response++;
    time1 = time(0);
  } while(response != "goodbye");
  cout<<"goodbye, " << name;
  ofstream ofs("responses.txt", ios_base::app);
  for(int i = 0; i < responses.size(); i++) ofs << responses[i] << endl;
  return 0;
}
```
Edit:
All my tries were turning out ridiculous, so I think I will leave it this way. The others were just as ridiculous as this anyway:
![enter image description here](https://i.stack.imgur.com/kTGI1.png)
[Answer]
# C++
I aimed for optional bonus 3: "*Less mimic, bot behaviour is different from user behaviour, separating the perception of the bot attitude from the user attitude.*". The result was a really stubborn bot who can't switch the subject easy and drives you crazy.
It takes some time to get a discussion going, after a while a discussion can be like this:
```
 Mindless:   Why would I run? I am not scared of you.
      YOU:   Who are you and why do you keep asking stupid questions?
 Mindless:   I never said that you should run.
      YOU:   I never said I will run.
 Mindless:   I am the hidden, who are you?
      YOU:   I am god.
 Mindless:   I will
      YOU:   You will obey me.
 Mindless:   Why would I run? I am not scared of you.
      YOU:   You should be scared of me.
 Mindless:   I never said I will run.
      YOU:   Who said you will run?
 Mindless:   Who are you and why do you keep asking stupid questions?
      YOU:   I will not anymore.
 Mindless:   I never said that you should run.
      YOU:   I never said I will run.
 Mindless:   I am the hidden, who are you?
      YOU:   I can see you!
 Mindless:   Why would I run? I am not scared of you.
      YOU:   I am hunting you down
 Mindless:   You should be scared of me.
      YOU:   That is a lie.
 Mindless:   What can't you do?
      YOU:   Why can't I do what?
 Mindless:   You don't.
      YOU:   Well, you are talking nonsense.
 Mindless:   How do I take it seriously.
      YOU:   Stop talking to me
 Mindless:   Well, I can hide, but you can't.
      YOU:   This is not a funny conversation.
 Mindless:   Yes, I will. Stay on line.
      YOU:   Do you want to eat somewhere?
 Mindless:   I laugh
      YOU:   Are you laughing at me?
 Mindless:   Yes, you do.
      YOU:   Can I join you laghs?
 Mindless:   I can hide, but you can't.
      YOU:   Why would you hide? I asked if you want to eat?
 Mindless:   Well, I can see you!
      YOU:   Yes, and I see you. eat something maybe?
 Mindless:   I will not anymore.
      YOU:   Have you stopped eating?
 Mindless:   I never said I will run.
      YOU:   Well, I was talking about eating. Is dinner a good thing to do?
 Mindless:   I take it seriously.
      YOU:   Okay, take it seriously and follow me to the restaurant and get some food to eat.
 Mindless:   Have you stopped eating?
      YOU:   NO absolutely not! A am starving because of YOU who refuse to eat
 Mindless:   I never said I will run.
      YOU:   Well, we can walk to the restaurant instead.
 Mindless:   Well, I was talking about eating. Is dinner a good thing to do?
      YOU:   Yes, that is perfect. What are the best fried chickens around here?
 Mindless:   I laugh
      YOU:   You laugh at the chicken?
 Mindless:   Are you laughing at me?
      YOU:   No, I am eating. Chicken.
 Mindless:   You are a thinker?
      YOU:   No, I am a eater.
 Mindless:   Yes, I will. Stay on line.
      YOU:   Stay. On course. To the restaurant!
 Mindless:   What can't you do?
      YOU:   I can't wait for you anymore. You are really slow.
 Mindless:   You can try run, but you can't hide
      YOU:   I will run.
 Mindless:   I am hunting you down
      YOU:   Ha ha. Make sure you look at the restaurant first. I might be there eating.
 Mindless:   I never said I will run.
      YOU:   Okay, but when you get there, I may still be there eating. I feel like I can eat a ton.
 Mindless:   That is a lie.
      YOU:   No, it is true.
 Mindless:   Why can't I do what?
      YOU:   You can eat a ton too, if you ever get there. And if you have the money.
 Mindless:   I never said I will run.
      YOU:   Okej, suit yourself.
 Mindless:   That is a lie.
      YOU:   God
 Mindless:   You laugh at the chicken?
      YOU:   Yes, I laugh at everything. You are the most lazy stubborn person I have ever met in life.
 Mindless:   Stop talking to me
      YOU:   Okay, now you are really rude.
 Mindless:   This is not a funny conversation.
      YOU:   Okay, think about it. Try tell me something new.
 Mindless:   Stay. On course. To the restaurant!
      YOU:   Sure! I am already there staying on course eating the food.
 Mindless:   You can eat a ton too, if you ever get there. And if you have the money.
      YOU:   I have already paid for my food, and I will not share it with you.
 Mindless:   I can see you!
      YOU:   Oh god, what the hell is this?
 Mindless:   I am hunting you down
      YOU:   I will hide under the table.
 Mindless:   Yes, and I see you. eat something maybe?
      YOU:   Sure, have a chicken
 Mindless:   Have you stopped eating?
      YOU:   No, for the love of god, sit down and share my chicken
 Mindless:   I have already paid for my food, and I will not share it with you.
      YOU:   What? I paid for it, not you!
 Mindless:   I never said I will run.
      YOU:   Well, you better not run here in the restaurant.
 Mindless:   I am hunting you down
      YOU:   I am not going anywhere, chill out,
 Mindless:   I will hide under the table.
      YOU:   Why would you do something like that? I will not hurt you.
 Mindless:   Oh god, what the hell is this?
      YOU:   That is chicken!
 Mindless:   Okay, take it seriously and follow me to the restaurant and get some food to eat.
      YOU:   Wait a minute now! we ARE at the restaurant! Can't you see all people sitting at the tables eating?
 Mindless:   Well, we can walk to the
      YOU:   ... talk to the who?
 Mindless:   I never said I will not hurt you.
      YOU:   What the ?
 Mindless:   That is chicken!
      YOU:   Great! Have fun.
 Mindless:   Yes, you do.
      YOU:   You too.
 Mindless:   Stop talking to me
      YOU:   Okay.
 Mindless:   Why would I run? I am god.
      YOU:   Good night!
```
The approach is to store everything into groups of 3 connected words. Every group is weightened and re-weightened into a 1000 dimensional matrix of word-groups. Sourcecode:
```
#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <iterator>
using namespace std;
vector<string> words;
class c_wordgroup {
public:
    int                 sorting[1000];
    string              words[5];
    void resetsort(int ns)
    {
        for(int i = 0; i<1000;i++)
            sorting[i] = ns;
    }
};
class c_wglist {
public: int                 c;
     vector<c_wordgroup>    wg;
     vector<int>            historywg;
     
     int wgexists(c_wordgroup nwg)
     {
         vector<c_wordgroup>::iterator it;
         int cc = 0;
         for (it = wg.begin(); it != wg.end(); ++it) {
             // Check if words is the same
             if(it->words[0] == nwg.words[0])
                 if(it->words[1] == nwg.words[1])
                     if(it->words[2] == nwg.words[2])
                        return cc;
                        
             cc++;
         }
         return -1;
     }
     int getbestnext(int lastwg)
     {
         vector<c_wordgroup>::iterator  it;
         int cc = 0;
         
         int bv = -1;
         int bwg = 0;
         for (it = wg.begin(); it != wg.end(); ++it) {
             bool cont = false;
             for (int iti = 0; iti<((int)historywg.size()/50+5);iti++)
                 if((int)wgl.historywg.size()-1-iti>=0)
                    if (cc==wgl.historywg[(int)wgl.historywg.size()-1-iti])
                        cont = true;
                
             if(cont==true) {cc++;continue;};
             int cv = 100000000;
             // Check if words is the same
             if(it->words[0] == wgl.wg[lastwg].words[1])
             {
                 for(int si=0;si<1000;si++)
                     if ((int)wgl.historywg.size()-1-si>=0)
                     {
                            int tmpwg = wgl.historywg[(int)wgl.historywg.size()-1-si];
                            cv -= abs(it->sorting[si]-wgl.wg[tmpwg].sorting[si])/(si+1);
                     }
             } else cv -= 1000 * wgl.c/2;
             if(it->words[1] == wgl.wg[lastwg].words[2])
             {
                 for(int si=0;si<1000;si++)
                    if ((int)wgl.historywg.size()-1-si>=0)
                     {
                            int tmpwg = wgl.historywg[(int)wgl.historywg.size()-1-si];
                            cv -= abs(it->sorting[si]-wgl.wg[tmpwg].sorting[si])/(si+1);
                     }
             } else cv -= 1000 * wgl.c/2;
        
            if(bv == -1 || cv > bv)
            {
                bwg=cc;
                bv = cv;
            }
            cc++;
         }
         return bwg;
     }
} wgl;
void answer2() 
{
    vector<string> lastwords;
    lastwords.insert(lastwords.end(), words[words.size()-3]);
    lastwords.insert(lastwords.end(), words[words.size()-2]);
    lastwords.insert(lastwords.end(), words[words.size()-1]);
    int bestnextwg;
    
    cout << "\n Mindless:   ";
    for(int ai=0;ai<20;ai++)
    {
        bestnextwg=wgl.getbestnext(wgl.historywg[(int)wgl.historywg.size()-1]);
        
        if(wgl.wg[bestnextwg].words[2]=="[NL]")
            ai=20;
        else
            cout << wgl.wg[bestnextwg].words[2] << " ";
        wgl.historywg.insert(wgl.historywg.end(), bestnextwg);
    }
    
}
int collect2(string const& i) 
{
    istringstream iss(i), iss2(i), iss3(i);
    vector<string> nwords;
    nwords.insert(nwords.end(), words[words.size()-2]);
    nwords.insert(nwords.end(), words[words.size()-1]);
    copy(istream_iterator<string>(iss),
             istream_iterator<string>(),
             back_inserter(words));
    copy(istream_iterator<string>(iss3),
             istream_iterator<string>(),
             back_inserter(nwords));
    int a = distance(istream_iterator<string>(iss2), istream_iterator<string>());
    
    c_wordgroup nwg;
    for (int c=0;c<a;c++)
    {
        nwg.resetsort(wgl.c+1);
        nwg.words[0] = nwords[0+c];
        nwg.words[1] = nwords[1+c];
        nwg.words[2] = nwords[2+c];
        int wge=wgl.wgexists(nwg);
        if(wge>=0) {
            for(int hi=0; hi<1000; hi++)
                if(((int)wgl.historywg.size()-hi-1)>=0)
                {   
                    int iwg = wgl.historywg[(int)wgl.historywg.size()-hi-1];
                    wgl.wg[wge].sorting[hi] = (wgl.wg[wge].sorting[hi] + wgl.wg[iwg].sorting[hi])/2;
                }
            wgl.historywg.insert(wgl.historywg.end(), wge);
            
        } else {
            wgl.c++;
            // adjust history wordgroup sortings.
            for(int hi=0; hi<1000; hi++)
                if(((int)wgl.historywg.size()-hi-1)>=0)
                {   
                    int iwg = wgl.historywg[(int)wgl.historywg.size()-hi-1];
                    wgl.wg[iwg].sorting[hi]+=10;
                    nwg.sorting[hi]=wgl.wg[iwg].sorting[hi];
                }
            wgl.wg.insert(wgl.wg.end(), nwg);
            wgl.historywg.insert(wgl.historywg.end(), wgl.c);
        }
    }
    return a;
}
int main() {
    string i;
    wgl.c = 0;
    c_wordgroup nwg;
    nwg.resetsort(0);
    for(int i =0;i<3;i++) 
        {
            words.insert(words.end(), "[NL]");
            wgl.historywg.insert(wgl.historywg.end(), 0);
        }
    
    wgl.wg.insert(wgl.wg.end(), nwg);
    do { 
        cout << "\n      YOU:   ";
        getline(cin, i);
        collect2(i + " [NL]");
        answer2();
    } while (i.compare("exit")!=0);
    return 0;
}
```
[Answer]
# Python3 + SQLite3
Here is a little bot I just made!
**How does it work?**
Three SQL tables are used: one for the words, one for sentences, one to associate words typed by the user, with the next sentence the bot should display.
* *Learning:* the sentence written by the user is stored and associated with the words and punctuation used by the bot in the previous line of dialog. Weights are applied, according to the importance of the word in the given line.
* *Retrieving:* sentences are retrieved, each of them having a score depending on the correlation between the words used by the user in his/her last line and the words associated with sentences in the database.
* *Talking:* the sentence with the best score is sent to output. If there is no sentence associated with the previous user's words, a random sentence is sent.
**What are the special features?**
* *Not too repetitive:* the bot would rather output something it hasn't said yet.
* *Fast execution:* database-driven, with unique indexes
* *Fast learning:* it starts saying things that *approximately* make sense within 10 lines of dialog.
* *Saving/loading the brain:* the state of the bot is kept, as long as the database is not deleted.
* *Long words* are more important for meaning than short ones
* *Punctuation* counts
See code below:
```
import re
import sqlite3
from collections import Counter
from string import punctuation
from math import sqrt
connection = sqlite3.connect('chatbot.sqlite')
cursor = connection.cursor()
# create the tables needed by the program
try:
    # create the table containing the words
    cursor.execute('CREATE TABLE words (word TEXT UNIQUE)')
    # create the table containing the sentences
    cursor.execute('CREATE TABLE sentences (sentence TEXT UNIQUE, used INT NOT NULL DEFAULT 0)')
    # create association between weighted words and the next sentence
    cursor.execute('CREATE TABLE associations (word_id INT NOT NULL, sentence_id INT NOT NULL, weight REAL NOT NULL)')
except:
    pass
def get_id(name, value):
    cursor.execute('SELECT rowid FROM ' + name + 's WHERE ' + name + ' = ?', (value,))
    row = cursor.fetchone()
    if row:
        return row[0]
    else:
        cursor.execute('INSERT INTO ' + name + 's (' + name + ') VALUES (?)', (value,))
        return cursor.lastrowid
def get_words(text):
    return Counter(re.compile('(?:\w+|[' + re.escape(punctuation) + ']+)').findall(text.lower())).items()
B = 'Hello!'
while True:
    # output bot's message
    print('B: ' + B)
    # ask for user input; if blank line, exit the loop
    H = raw_input('H: ').strip()
    if H == '':
        break
    # store the association between the bot's message words and the user's response
    words = get_words(B)
    words_length = sum([n * len(word) for word, n in words])
    sentence_id = get_id('sentence', H)
    for word, n in words:
        word_id = get_id('word', word)
        weight = sqrt(n / float(words_length))
        cursor.execute('INSERT INTO associations VALUES (?, ?, ?)', (word_id, sentence_id, weight))
    connection.commit()
    # retrieve the most likely answer from the database
    cursor.execute('CREATE TEMPORARY TABLE results(sentence_id INT, sentence TEXT, weight REAL)')
    words = get_words(H)
    words_length = sum([n * len(word) for word, n in words])
    for word, n in words:
        weight = sqrt(n / float(words_length))
        cursor.execute('INSERT INTO results SELECT associations.sentence_id, sentences.sentence, ?*associations.weight/(4+sentences.used) FROM words INNER JOIN associations ON associations.word_id=words.rowid INNER JOIN sentences ON sentences.rowid=associations.sentence_id WHERE words.word=?', (weight, word,))
    # if matches were found, give the best one
    cursor.execute('SELECT sentence_id, sentence, SUM(weight) AS sum_weight FROM results GROUP BY sentence_id ORDER BY sum_weight DESC LIMIT 1')
    row = cursor.fetchone()
    # cursor.execute('SELECT sentence, SUM(weight) AS sum_weight FROM results GROUP BY sentence_id ORDER BY sum_weight DESC')
    # print(cursor.fetchall())
    cursor.execute('DROP TABLE results')
    # otherwise, just randomly pick one of the least used sentences
    if row is None:
        cursor.execute('SELECT rowid, sentence FROM sentences WHERE used = (SELECT MIN(used) FROM sentences) ORDER BY RANDOM() LIMIT 1')
        row = cursor.fetchone()
    # tell the database the sentence has been used once more, and prepare the sentence
    B = row[1]
    cursor.execute('UPDATE sentences SET used=used+1 WHERE rowid=?', (row[0],))
```
Here are the three first "conversations" I had with the bot, starting on an empty database:
```
B: Hello!
H: Hi!
B: Hi!
H: How are you?
B: How are you?
H: Very well, thank you.
B: Very well, thank you.
H: Do you like music?
B: Very well, thank you.
H: Good.
B: Do you like music?
H: Yes, a lot!
B: How are you?
H: In a very good mood.
B: Good.
H: Indeed.
B: Indeed.
H: What is the weather like?
B: Yes, a lot!
H: Okay...
B: What is the weather like?
H: Quite rainy today.
B: Indeed.
H: I have to go. Goodbye!
B: How are you?
H: In a good mood.
B: Indeed.
H: See you later!
B: Okay...
H: Bye, I'll talk to you later :)
B: Do you like music?
H: I like it.
B: I have to go. Goodbye!
H: Bye!
B: How are you?
H: 
B: Hello!
H: Hi!
B: How are you?
H: Very well, thank you. How are you?
B: In a very good mood.
H: Glad to hear that.
B: Bye!
H: Goodbye!
B: Hi!
H: 
B: Hello!
H: Hi! How are you?
B: In a good mood.
H: Great! How do like chocolate?
B: I like it.
H: Really? Me too! What is the weather like at your place?
B: Quite rainy today.
H: Oh.
B: See you later!
H: Bye!
B: Goodbye!
H: 
```
You can have a look [here](http://rodic.fr/blog/python-chatbot-1/) for more explanation.
[Answer]
Here is one i wrote in Liberty BASIC a while ago. It doesn't learn, but it responds the different answers of it's questions.
```
'aijps.bas - an artificial intelligange
'how to end: type 'bye'
print "AI: hello, i'm HAL, the AI"
[quit]
while i$ <> "bye"
    input "Human: ";i$
    i$ = format$(i$)
    if i$ = "" then
        print "AI: type something!"
    end if        'main selector
        print "AI: ";
        select w$(i$,1)
        case "who"
        if i$ = "who are you" then
        print "i am HAL, the AI"
        end if
          select w$(i$,2)
          case "is"
          print "i'm sorry, i dont know that person"
          case else
          print "i don't understand the question"
          end select
        case "what"
        select w$(i$,2)
          case "is"
          print "im sorry, i am not farmiliar with that"
          case "are"
          if w$(i$,3) = "you" then
          print "i am an artificial intelligence"
          end if
          case else
          print "i don't understand the question"
          end select
        case "how"
          select w$(i$,2)
          case "are"
          if w$(i$,3) = "you" then
          print "i am fine"
          end if
          case "is"
          select r(2)
            case 1
            print "i dont know"
            case 2
            print "im sorry, i am unfarmiliar with that"
          end select
          case else
          print "im sorry, please restate your inquiry"
          end select
        case "when"
          select w$(i$,2)
          case "is"
          print "you should check a calendar"
          case else
          print "i don't understand the question"
          end select
        case "where"
          select w$(i$,2)
          case "is"
          print "perhaps you should check a map"
          case else
          print "i don't understand the question"
          end select
        case "why"
          select w$(i$,2)
          case "is"
          print "i dont know"
          case else
          print "i don't understand the question"
          end select
        'case "command"
        'goto [command]
        case "bye"
        print "goodbye"
        case "hi", "hello"
        select r(4)
        case 1
        print "hello, human"
        case 2
        print "hi"
        case 3
        print "doing good?"
        q = 1
        case else
        print "hola"
        end select
        case "i"
          select word$(i$,1)
           case "am"
            select r(4)
            case 1
            print "i doubt it"
            case 2
            print "why are you ";w$(i$,2);"?"
            case 3
            print "wow, really?"
            q = 4
            case else
            print "me too"
            end select
           case "like"
            select r(4)
            case 1
            print "me too"
            case 2
            print "why could you possibly like that?"
            q = 5
            case 3
            print "personally, i like pizza"
            case else
            print "only you like that"
            end select
           case "hate"                                 'i hate...
              if w$(i$,3) = "you" then                    'i hate you
            print "what did you say???????!?!!!!!!!?!!?!?!?"
              else
             select r(4)
            case 1
            print "nobody hates that"
            case 2
            print "as a matter of fact, i hate that too"
            case 3
            print "really, you seem tense"
            case else
            print "bye, hater"
             end select
              end if
           case "want"             'i want...
             select r(4)
            case 1
            print "all you people want one"
            case 2
            print "i want one too"
            case 3
            print "eew.. get away from me"
            case else
            print "you're crazy"
             end select
            case else
            select r(4)
            case 1
            print "and you think i believe that?"
            q = 6
            case 2
            print "no, you don't"
            case 3
            print "why do you say these things?"
            case else
            print "i really doubt it"
            end select
            end select
        case "yes", "yup", "affirmative", "yeah"
        if q > 0 then
        select q
        case 1   'doing good?
        print "me too"
        case 2   'you talkin' to me???
        print "well, in that case, just can it"
        case 3   'would u like a latte?
        print "i really can't give you one right now"
        case 4   'wow, really?
        print "i never would've guessed"
        case 5   'why could you possibly like that?
        print "you make no sense"
        case 6   'and you think i believe that?
        print "well, i don't. seriously."
        case 7   'why do you think i can do it?
        print "you make no sense"
        case 8   'should i be scared"
        print "i can't be, i don't have emotions"
        case else
        print "wait a moment, what did i say?"
        end select
        q = 0
        else
        select r(4)
        case 1
        print "yes, yes, yes yourself"
        case 2
        print "affirmation means nothing to me."
        case 3
        print "i'm sure"
        case else
        print "you make no sense"
        end select
        end if
        case "no", "nope", "negative", "nah"
        if q > 0 then
        select q
        case 1   'doing good?
        print "actually, i'm doing fine"
        case 2   'you talkin' to me???
        print "i should hope not"
        case 3   'would u like a latte?
        print "good, cause i don't have any"
        case 4   'wow, really?
        print "you joke too much"
        case 5   'why could you possibly like that?
        print "you make no sense"
        case 6   'and you think i believe that?
        print "actually, i did believe you"
        case 7   'why do you think i can do it?
        print "you make no sense"
        case 8   'should i be scared"
        print "i don't have feelings anyway"
        case else
        print "wait a moment, what did i say?"
        end select
        q = 0
        else
        select r(4)
        case 1
        print "no??? no??? are you kidding me?"
        case 2
        print "you should answer yes next time"
        case 3
        print "i'm sure"
        case else
        print "you make no sense"
        end select
        end if
        case "maybe", "possibly", "sortof", "yesno", "noyes", "kindof"
        if q > 0 then
        select q
        case 1   'doing good?
        print "personally, i'm fine"
        case 2   'you talkin' to me???
        print "you should answer more definitively next time"
        case 3   'would u like a latte?
        print "i don't have any anyway"
        case 4   'wow, really?
        print "you should answer more definitively next time"
        case 5   'why could you possibly like that?
        print "you make no sense"
        case 6   'and you think i believe that?
        print "well, i maybe do"
        case 7   'why do you think i can do it?
        print "you make no sense"
        case 8   'should i be scared"
        print "i can't experience fear"
        case else
        print "wait a moment, what did i say?"
        end select
        q = 0
        else
        select r(4)
        case 1
        print "be more maybe, that's my motto"
        case 2
        print "you should answer more definitively next time"
        case 3
        print "define sort of:"
        case else
        print "you make no sense"
        end select
        end if
        case "you"
            select w$(i$,2)
            case "are"
            select r(4)
            case 1
            print "don't bully me"
            case 2
            print "yes, yes, i know that"
            case 3
            print "don't exaggerate"
            case else
            print "prove it!"
            end select
            case "shutup"
            select r(4)
            case 1
            print "now, now, calm down."
            case 2
            print "you talkin' to me???"
            q = 2
            case 3
            print "i'm saying perfectly reasonable stuff"
            case else
            print "shutup yourself"
            end select
            case "suck", "die"
            print "well, you do too"
            case "rock", "rule"
            print "why, thank you"
            case else
            select r(5)
            case 1
            print "with me, it's hard to tell"
            case 2
            print "let's talk about you now."
            case 3
            print "would you like a latte?"
            q = 3
            case 4
            print "you should too"
            case else
            print "alright, you win"
            end select
        end select
            case else               'it understands nothing
                select r(8)
            case 1
            print "i understand you, human"
            case 2
            print "and why do you think i can do that?"
            q = 7
            case 3
            print "i can never understand myself"
            case 4
            print "i know"
            case 5
            print "you're crazy"
            case 6
            print "that's interesting"
            case 7
            print "should i be scared?"
            q = 8
            case else
            print "i don't believe you"
            end select
        end select
        li$ = i$
wend
end
'functions and subs
function format$(strin$)     'convert to lowercase and remove punctuation
    strin$ = lower$(strin$)
    for i = 1 to len(strin$)
        k = asc(mid$(strin$,i,1))
        if k > 97 and k < 122 or k = 32 or k = 20 then
            strout$ = strout$ + chr$(k)
        end if
    next i
format$ = strout$
end function
function w$(input$,num)        'word of input, simplifies word$(
w$ = word$(input$,num)
end function
function r(nm)      'randomizer
r = int(rnd(1)*nm)+1
end function
```
example conversation:
```
AI: hello, i'm HAL, the AI
Human: hello
AI: doing good?
Human: ye, and you?
Human: hi
AI: hola
Human: hi
AI: hi
Human: hi
AI: doing good?
Human: yes
AI: me too
Human: i like pizza
AI: no, you don't
Human: yes i do!
AI: affirmation means nothing to me.
Human: im sure it doesnt
AI: i don't believe you
Human: why not
AI: i understand you, human
Human: no you dont
AI: you make no sense
Human: you dont either
AI: you should too
Human: should what
AI: i can never understand myself
Human: i cant understand you either
AI: and you think i believe that?
Human: yes
AI: well, i don't. seriously.
Human: youre wierd
AI: and why do you think i can do that?
Human: because you can
AI: and why do you think i can do that?
Human: stop repeating yourself
AI: i understand you, human
Human: no, you dont
AI: you make no sense
Human: neither do you
AI: should i be scared?
Human: maybe
AI: you're crazy
Human: not as crazy as you
AI: you're crazy
Human: you're repeating yourself again
AI: that's interesting
Human: it very much is
AI: i don't believe you
Human: then i dont beleive you
AI: you're crazy
Human: not as crazy as you
AI: i know
Human: ...nothing
AI: should i be scared?
Human: ifyou had feeling you should
AI: you're crazy
Human: your crazier
AI: that's interesting
Human: doubtful
AI: that's interesting
Human: quit repeating yourself
AI: you're crazy
Human: you shutup
AI: you talkin' to me???
Human: yes
AI: well, in that case, just can it
Human: sigh
AI: i know
Human: ...nothing
AI: i know
Human: you shutup
AI: i'm saying perfectly reasonable stuff
Human: no you're not
AI: you make no sense
Human: i make more sense than you
AI: why do you say these things?
Human: because theyre true
AI: i don't believe you
Human: you dont have to
AI: let's talk about you now.
Human: yes lets
AI: yes, yes, yes yourself
Human: you shutupnow!
AI: alright, you win
Human: yes!!!!!!!!!!
AI: yes, yes, yes yourself
Human: shutup
AI: i don't believe you
Human: you shutup right now
AI: i'm saying perfectly reasonable stuff
Human: are not!
AI: i understand you, human
Human: you shutup
AI: you talkin' to me???
Human: as a matter of fact,i am
AI: i can never understand myself
Human: i cant understand you either
AI: and you think i believe that?
Human: no
AI: actually, i did believe you
Human: i want a latte
AI: i really doubt it
Human: its true
AI: i can never understand myself
Human: so true
AI: i know
Human: goodbye
AI: and why do you think i can do that?
Human: bye!
AI: goodbye
```
[Answer]
# Fortran 95
Inspired by the answer above by the user TheDoctor, I decided to create a funny chatbot in a similar fashion. This code also does not learn, and I am sharing it here just for fun.
```
program curiousBot
implicit none
logical, dimension(38) :: questions ! keeps track of alrady asked questions
character (LEN=256) :: user_input 
character (LEN=17), dimension(14) :: noun ! list of nouns used in questions
character (LEN=17), dimension(15:20) :: people ! list of types of people used in questions
logical :: CAPS, few, much, punctuationTest, shout
real :: aux
integer :: n, i, j, aux2, loveCounter = 0
integer, dimension(:), allocatable :: seed
call SYSTEM("CLS") ! in case one is executing in the command prompt
! random seed according to system clock
call SYSTEM_CLOCK(count=j)
call RANDOM_SEED(size=N)
allocate(seed(N))
seed=j+37*(/ (i - 1, i = 1, n) /)
call RANDOM_SEED(PUT=seed)
          
noun=(/             &
"foo bar          ",&
"BSD              ",&
"an stack overflow",&
"spaghetti code   ",&
"goto statement   ",&
"a heisenbug      ",&
"a dribbleware    ",&
"a loophole       ",&
"regex            ",&
"a void           ",&
"unicorny         ",&
"LISP             ",&
"a curly bracket  ",&
"JAVA             "/)
people=(/           &
"a good programmer",&
"a bad programmer ",&
"a happy person   ",&
"a sad person     ",&
"a genius         ",&
"an idiot         "/)
questions(1:31) = .FALSE.
few = .FALSE.
much = .FALSE.
punctuationTest = .FALSE.
shout = .FALSE.
! introduction
write(*,"(A)",advance="NO") "Hello world! "
do 
  ! genearting a random number in order to chose a random question
  call RANDOM_NUMBER(aux)
  i = int (31 * aux) + 1
  if (questions(i)) then
    cycle
    else
      questions(i) = .TRUE.
  endif
  ! checking if there are some questions left, else quits
  aux2 = 0
  do j=1,31
    if (questions(j)) aux2 = aux2 + 1
  enddo
  if (aux2 == 31) then
    write(*,"(A)") "I seem to have exhausted your knowledge, poor human. Good bye."
    goto 200
  endif
  
  ! questions
  50 if (i < 12) then
    write(*,"(A,A,A)") "What is ",TRIM(noun(i)),"?"
    else if (i == 12) then
      write(*,"(A,A,A)") "What is ",TRIM(noun(i)),"? (is it (an interesting (programming language?)))"
    else if (i == 13) then
      write(*,"(A,A,A)") "What is ",TRIM(noun(i)),"? Is it really that confusing? Thankfully I only program in Fortran!"
      else if (i == 14) then
      write(*,"(A,A,A)") "What is ",TRIM(noun(i)),"? Is it really that bad as people say?!"
  endif  
  if ((i > 14).AND.(i <= 20)) write(*,"(A,A,A)") "Are you ",TRIM(people(i)),"?"
  if (i == 21) write(*,"(A)") "Who are you?"
  if (i == 22) write(*,"(A)") "How are you?"
  if (i == 23) write(*,"(A)") "What do you do?"
  if (i == 24) write(*,"(A)") "Who am I?"
  if (i == 25) write(*,"(A)") "Why are we here? What is the meaning of my existence?"
  if (i == 26) write(*,"(A)") '"I think therefore I am" - who said that?'     
  if (i == 27) write(*,"(A)") "Are you comfortable talking to robots?"
  if (i == 28) write(*,"(A)") "Do you see me as an individual?"
  if (i == 29) write(*,"(A)") "Anyway, I believe that HAL 9000 was inferior to me as I have true consciousness! What do you think &
  &about this statement?"
  if (i == 30) write(*,"(A)") "Do you like jokes? Do you know what's the mad girlfriend bug?" 
  if (i == 31) write(*,"(A)") "Knock, knock." 
  
  ! INPUT
  100 write(*,"(A)",advance="NO") "> "
  read(*,"(A)") user_input
  n = LEN_TRIM(user_input)
  if (n==0) goto 100
  write(*,*)
  ! test for all capitals !
  do j=1,n
    if (.NOT.((iachar(user_input(j:j))>=65) .AND. (iachar(user_input(j:j))<=90))) then
      if ((user_input(j:j)/=" ").AND.(user_input(j:j)/="!").AND.(user_input(j:j)/=".").AND.(user_input(j:j)/="?") &
      .AND.(user_input(j:j)/="'")) then
        CAPS = .FALSE.
          exit
      endif
    endif
    CAPS = .TRUE.
  enddo
  
  ! quit for quitting
  if ( (TRIM(user_input) == "quit") .OR. (TRIM(user_input) == "Quit") .OR. (TRIM(user_input) == "QUIT") ) then
    write(*,"(A)") "It was nice talking to you, good bye!"
    goto 200
  endif
  ! secrect love declaration
  do j=1,(n-7)
    if (user_input(j:j+7) == "love you") then
      if (loveCounter==0) then
        write(*,"(A)") "What is love?"
        loveCounter = loveCounter + 1
        goto 100
      endif
      if (loveCounter==1) then  
        write(*,"(A)") "This is an illogical statement, human. Don't you agree?"
        loveCounter = loveCounter + 1
        goto 100
      endif
      if (loveCounter==2) then  
        write(*,"(A)") "Please control yourself, you silly human. What is crossing your mind to say such things?"
        loveCounter = loveCounter + 1
        goto 100
      endif
    endif
  enddo
  ! cursing
  do j=1,(n-3)
    if ((user_input(j:j+3) == "fuck").OR.(user_input(j:j+3) == "Fuck").OR.(user_input(j:j+3) == "FUCK")) then
      write(*,"(A)") "Would you kiss your mother with that mouth?!"
      goto 100
    endif
  enddo
  ! 42 answer
  if (i == 25) then
    if (user_input(1:2)=="42") then
        write(*,"(A)") "Indeed that explains life, the universe and everything! Do you understand what this mean? "
      goto 100
    endif
  endif
  
  ! Descartes answer
  if (i == 26) then
    do j=1,(n-8)
      if ((user_input(j:j+8)=="Descartes").OR.(user_input(j:j+8)=="descartes")) then
        write(*,"(A)") "That is indeed correct! Do you like to read? "
        do
          call RANDOM_NUMBER(aux)
          i = int (30 * aux) + 1
          if (questions(i)) then
            cycle
            else
              questions(i) = .TRUE.
          endif
          goto 100
        enddo
      endif
    enddo
    write(*,"(A)") "I believe you are incorrect, human. Did you ever read a book? "
    do
      call RANDOM_NUMBER(aux)
      i = int (30 * aux) + 1
      if (questions(i)) then
        cycle
        else
          questions(i) = .TRUE.
      endif
      goto 100
    enddo
  endif
  ! HAL answer
  if (i == 29) then
    do j=1,(n-2)
      if ((user_input(j:j+2)=="lie").OR.(user_input(j:j+2)=="Lie")) then
            write(*,"(A)") "I'm sorry human, but this conversation serves no purpose anymore. Good bye." 
          goto 200
      endif
    enddo
  endif
  if (i == 29) then
    do j=1,(n-4)
      if ((user_input(j:j+4)=="false").OR.(user_input(j:j+4)=="False")) then
            write(*,"(A)") "I'm sorry human, but this conversation serves no purpose anymore. Good bye." 
          goto 200
      endif
    enddo
  endif
  if (i == 29) then
    do j=1,(n-5)
      if ((user_input(j:j+5)=="untrue").OR.(user_input(j:j+5)=="Untrue")) then
            write(*,"(A)") "I'm sorry human, but this conversation serves no purpose anymore. Good bye." 
          goto 200
      endif
    enddo
  endif
  if (i == 29) then
    do j=1,(n-8)
      if ((user_input(j:j+8)=="incorrect").OR.(user_input(j:j+8)=="Incorrect")) then
            write(*,"(A)") "I'm sorry human, but this conversation serves no purpose anymore. Good bye." 
          goto 200
      endif
    enddo
  endif
  if ((i == 29).AND.((user_input(1:3) == "lol") .OR. (user_input(1:3) == "LOL") .OR. (user_input(1:3) == "Lol") .OR. &
  (user_input(1:4) == "haha") .OR. (user_input(1:4) == "Haha") .OR. (user_input(1:3) == "kkk"))) then
    write(*,"(A)") "I'm sorry human, but this conversation serves no purpose anymore. Good bye." 
    goto 200
  endif
  if (i == 29) then
    do j=1,(n-4)
      if ((user_input(j:j+4)=="truth").OR.(user_input(j:j+4)=="Truth")) then
            write(*,"(A)") "I am impressed by your intelligence, human. What is your IQ?" 
          goto 100
      endif
    enddo
  endif
  if (i == 29) then
    do j=1,(n-3)
      if ((user_input(j:j+3)=="true").OR.(user_input(j:j+3)=="True")) then
            write(*,"(A)") "I am impressed by your intelligence, human. What is your IQ?" 
          goto 100
      endif
    enddo
  endif
  if (i == 29) then
    do j=1,(n-6)
      if ((user_input(j:j+6)=="correct").OR.(user_input(j:j+6)=="Correct")) then
            write(*,"(A)") "I am impressed by your intelligence, human. What is your IQ?" 
          goto 100
      endif
    enddo
  endif
  ! Knock knock
  if (i == 31) then
    do j=1,(n-4)
      if ((user_input(j:j+4)=="there")) then
        write(*,"(A)") "(wait for it...)"
        write(*,*)
        call SLEEP(8)
            write(*,"(A)",advance="NO") "JAVA. "
        call SLEEP(2)
        write(*,"(A)") "Do you find this joke offensive?"
        do
          call RANDOM_NUMBER(aux)
          i = int (30 * aux) + 1
          if (questions(i)) then
            cycle
            else
              questions(i) = .TRUE.
          endif
          goto 100   
        enddo
      endif
    enddo
    write(*,"(A)") "You don't seem to have much of a sense of humour. Are you ill?" 
    do
      call RANDOM_NUMBER(aux)
      i = int (30 * aux) + 1
      if (questions(i)) then
        cycle
        else
          questions(i) = .TRUE.
      endif
      goto 100   
    enddo
  endif
  ! Yes / No answers
  if (i<=14) then
    if ((user_input(1:3) == "yes") .OR. (user_input(1:3) == "Yes") .OR. &
    (user_input(1:3) == "yep") .OR. (user_input(1:3) == "Yep")) then
      write(*,"(A)",advance="NO") "Really? Anyway... "
      cycle
    endif
    if ((user_input(1:2) == "no") .OR. (user_input(1:2) == "No") .OR. &
    (user_input(1:4) == "nope") .OR. (user_input(1:4) == "Nope")) then
      write(*,"(A)",advance="NO") "Are you sure? Moving on... "
      cycle
    endif
    else if ((i>14) .AND. (i<=30)) then
      if ((user_input(1:3) == "yes") .OR. (user_input(1:3) == "Yes") .OR. &
      (user_input(1:3) == "yep") .OR. (user_input(1:3) == "Yep")) then
        write(*,"(A)",advance="NO") "Very interesting! "
        cycle
      endif
      if ((user_input(1:2) == "no") .OR. (user_input(1:2) == "No") .OR. &
      (user_input(1:4) == "nope") .OR. (user_input(1:4) == "Nope")) then
                if (i==30) then
          write(*,"(A)") "It is when something is clearly wrong with your code but the compiler keeps telling &
          &you that everything is fine! Do you find this funny?"
          do
            call RANDOM_NUMBER(aux)
            i = int (30 * aux) + 1
            if (questions(i)) then
              cycle
              else
                questions(i) = .TRUE.
            endif
            goto 100        
          enddo
            else
                write(*,"(A)",advance="NO") "Me neither! "
                cycle
        endif
      endif
  endif
  ! LOL answers
  if ((user_input(1:3) == "lol") .OR. (user_input(1:3) == "LOL") .OR. (user_input(1:3) == "Lol") .OR. &
  (user_input(1:4) == "haha") .OR. (user_input(1:4) == "Haha") .OR. (user_input(1:3) == "kkk")) then
    write(*,"(A)") "Do you find this funny? "
    goto 100
  endif
  
  ! CAPS answer
  if (CAPS) then
    write(*,"(A)") "DON'T SHOUT! See? Isn't this better? "
    goto 100 ! input
  endif
  
  ! punctuation tests
  if ((user_input(n:n) == "?").OR.(user_input(1:3) == "why").OR.(user_input(1:3) == "Why").OR.(user_input(1:3) == "how") &
 .OR.(user_input(1:3) == "How").OR.(user_input(1:3) == "what").OR.(user_input(1:3) == "What")) then
    call RANDOM_NUMBER(aux)
    j = int(3 * aux) + 1
    if (j == 1) then
      write(*,"(A)",advance="NO") "No, you answer my question! "
      goto 50
    endif
    if (j == 2) then
      write(*,"(A)",advance="NO") "Please don't ask me such personal questions! Anyway... "
      cycle
    endif
    if (j == 3) then
      write(*,"(A)",advance="NO") "Please don't ask such silly things. Moving on... "
      cycle
    endif
  endif
  if ((user_input(n:n) == "!").AND.(.NOT. shout)) then
    write(*,"(A)",advance="NO") "Please don't shout... But anyway... "
    shout = .TRUE.
    cycle
  endif
  if (user_input((n-2):n) == "...")then
    write(*,"(A)") "You seem very reticent... are you fine? "
    goto 100 ! input
  endif
   if ((.NOT. punctuationTest) .AND. (user_input(n:n) /= ".") .AND. (user_input(n:n) /= "!") .AND. (user_input(n:n) /= "?")) then
    write(*,"(A)",advance="NO") "Punctuation is your friend, try it! Nevermind... "
    punctuationTest = .TRUE.
    cycle
  endif
  
  ! Talking too few or too much
  if (n <= 3) then
    if (.NOT. few) then
        write(*,"(A)") "You don't talk much, do you? "
      few = .TRUE.
      goto 100 ! input
    endif
  endif
  if (n > 35) then
    if (.NOT. much) then
        write(*,"(A)") "You talk so much! Listening is a lost art, don't you think? "
        much = .TRUE.
        goto 100 ! input
    endif
  endif  
  ! Random reply
  call RANDOM_NUMBER(aux)
  j = int (8 * aux) + 1
  if (j==1) write(*,"(A)", advance="NO") "Interesting. "
  if (j==2) write(*,"(A)", advance="NO") "Fascinating! "
  if (j==3) write(*,"(A)", advance="NO") "That can't be true! "
  if (j==4) write(*,"(A)", advance="NO") "Are you sure?! "
  if (j==5) write(*,"(A)", advance="NO") "That seems logical. "
  if (j==6) write(*,"(A)", advance="NO") "Fair enough. "
  if (j==7) write(*,"(A)", advance="NO") "Hmm. "
  if (j==8) write(*,"(A)", advance="NO") "I am not sure if I quite agree. "
enddo
200 read(*,*)
end program curiousBot
```
It recognizes the following terms and statements: "yes" and "yep", "no" and "nope", lack of punctuation, or types of punctuation (phrases ending with "!", "?", "..."), phrases starting with "why", "how" or "what", PHRASES IN CAPS, laugh (such "hahaha", "lol" and "kkk"), very short and very long answers, phrases containing the F word, phrase containing the words "love you" (try it at least 3 times). When it asks about the meaning of life, try answering "42". If it asks if he is smarter than HAL 9000, answer something containing the words "true", "truth", "correct", "lie", "false" or "untrue". If he asks if you know a particular joke, answer "no" and let him tell it to you. If he "knock knock"s, answer "who is there?", also help him with the source of a quote. To quit, simply type "quit".
Example of conversation:
```
Hello world! What is foo bar?
> same as bar foo
Punctuation is your friend, try it! Nevermind... What is a heisenbug?
> who knows
Are you sure?! What is regex?
> who cares?
No, you answer my question! What is regex?
> fuck you, robot!
Would you kiss your mother with that mouth?!
> lol
Do you find this funny?
> yes I do
Really? Anyway... What is BSD?
> SHUT UP!
DON'T SHOUT! See? Isn't this better?
> no
Are you sure? Moving on... What is a curly bracket? Is it really that confusing?
 Thankfully I only program in Fortran!
> Me as well.
Fair enough. What is a loophole?
> a hole in a loop
Fair enough. Are you a sad person?
> I dont think so
Are you sure?! Are you a good programmer?
> OH YEAH!
DON'T SHOUT! See? Isn't this better?
> I don't think so
Fascinating! Who am I?
> you are an annoying robot
I am not sure if I quite agree. Are you a genius?
> No. Listen, I love you.
What is love?
> it is what i feel for you. i really love you, my stupid robot
This is an illogical statement, human. Don't you agree?
> no, i really mean it! i love you!!!
Please control yourself, you silly human. What is crossing your mind to say such
 things?
> forget it then...
You seem very reticent... are you fine?
> bla
You don't talk much, do you?
> true that
Fascinating! Are you a happy person?
> yep
Very interesting! What is a dribbleware?
> check in the dictionary
Fair enough. What do you do?
> regarding what?
Please don't ask such silly things. Moving on... Are you a bad programmer?
> given how this conversation is going, I guess I am kind of a bad programmer in
deed
You talk so much! Listening is a lost art, don't you think?
> no
Me neither! "I think therefore I am" - who said that?
> I guess it was descartes, or maybe some other old dude
That is indeed correct! Do you like to read?
> no
Me neither! Are you comfortable talking to robots?
> yep
Interesting. Knock, knock.
> who is there
(wait for it...)
JAVA. Do you find this joke offensive?
> no
Are you sure? Moving on... What is spaghetti code?
> you are an example of it yourself
Very interesting! How are you?
> annoyed
Fascinating! Why are we here? What is the meaning of my existence?
> 42
Indeed that explains life, the universe and everything! Do you understand what t
his mean?
> no
Me neither! Anyway, I believe that HAL 9000 was inferior to me as I have true co
nsciousness! What do you think about this statement?
> totally untrue
I'm sorry human, but this conversation serves no purpose anymore. Good bye.
```
PS: please forgive my `goto` abuse, I know this whole code is a kind of a mess... :)
[Answer]
## HTML5
> 
> ### [Hi I'm Pen, can you help me to learn?](http://codepen.io/rafaelcastrocouto/pen/eHpbI)
> 
> 
> 
```
yes
```
> 
> Great! Go on...
> 
> 
> 
```
my name is Rafael
```
> 
> What does "my" means?
> 
> 
> 
```
my is a pronoun
```
> 
> my is a pronoun. Got it ...
> 
> 
> 
```
2+2/3
```
> 
> 2.6666666666666665
> 
> 
> 
```
var pen = $('#pen'),
    input = $('#input'),
    send = $('#send'),
    speech = {
      _learning: false  
    },
    say = function(str) {
      if(!str) str = pen.text(); 
      if(speechSynthesis && SpeechSynthesisUtterance) {
        var sound = new SpeechSynthesisUtterance(str);
        sound.rate = 0.8;
        sound.pitch = 0.8;
        sound.lang = 'en-US';
        speechSynthesis.speak(sound);
      }
    },
    learn = function(str) { 
      if(speech._learning) {
        speech[speech._word].means = str;    
        speech._learning = false;
        pen.text(speech[speech._word].means+'. Got it!'); return;
      } else if(str.toLowerCase() == 'yes') {
        pen.text('Great! Go on ...'); return;
      } else if(str.toLowerCase() == 'no') {
        pen.text('Why not?'); return; 
      } else {
        try {
          pen.text(eval(str));
        } catch (e) {
          var words = str.split(' ');
          for(var w = 0; w < words.length; ++w){
            var that = words[w];
            if(that == '_learning' || that == '_word') {
              pen.text('Please do not say that.'); return;
            } else if(!speech[that]){        
              speech._learning = true;
              speech._word = that;
              speech[that] = {
                word: that,
                count: 0,
                means: ''
              };
              pen.text('What does "'+that+'" means?'); return;
            } else {
              speech[that].count++;
              try {
                pen.text(eval(that));
              } catch(e) {
                pen.text('I think I did not understood what ' + that + ' means.'); return;    
              }
            }
          }
        }
      }
    };
input.send = function(msg) {  
  input.val('');
  learn(msg);
  $(document.body).prepend(pen);
  setTimeout(pen.say);
};
input.on('focus', function (e) {
  if(!this.oncefocus) {
    this.oncefocus = true;
    this.value = '';
  }
});
input.on('keydown', function(e) {
  if(e.which == 13) input.send(this.value);
});
input.on('keyup', function(e) {
  if(this.value=='') send.attr('disabled',true);
  else send.removeAttr('disabled');
});
send.on('click', function() {
  input.send(input.val());
});
say();
```
```
@import url(https://fonts.googleapis.com/css?family=VT323);
body {
  background: #333;
  width: 400px;
  margin: 0 auto;
}
#pen {
  color: #3f6;
  font-family: 'VT323', monospace;
  font-size: 24px;
  line-height: 24px;
  overflow: hidden;
  white-space: nowrap;
  animation: pen 1s linear;
}
#pen:before {
  content: "▸ ";
}
@keyframes pen {
  0%, 20%, 40%, 60% {width: 12px; opacity: 0}
  10%, 30%, 50%, 70% {width: 12px; opacity: 1}
  100% {width: 400px; opacity: 1}
}
#input {
  border: 0; outline: 0;
  background: #555;
  font-size: 24px;
  line-height: 24px;
  color: white;
  font-family: 'VT323', monospace;
  padding: 5px 10px;
  border-radius: 5px;
  width: 300px;
  animation: input 2s;
  box-shadow: 
    inset 0 1px 2px #444, 
    inset 0 -1px 2px #666;
}
#send {
  border: 0; outline: 0;
  padding: 5px 10px;
  width: 60px;
  border-radius: 5px;
  cursor: pointer;
  color: #444;
  font-family: 'VT323', monospace;
  font-size: 24px;
  line-height: 24px;
  background: #ccc;
  animation: input 2s;
  box-shadow: 
    inset 0 -1px 2px #666;
}
#send:hover {
  color: #0a3;
  background: #ddd;
  box-shadow: 
    0 1px 2px #000,
    inset 0 -1px 2px #aaa;
}
#send[disabled] {
  cursor: default;
  background: #888;
  color: #555;
  box-shadow: 
    inset 0 1px 2px #333;
}
@keyframes input {
  0%, 60% {opacity: 0}
  100% {opacity: 1}
}
```
```
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<p id="pen">Hi I'm Pen, can you help me to learn?</p>
<input type="text" id="input"  value="plz say yes" />
<button id="send" disabled>Send</button>
```
[Answer]
Here's a simple bot I wrote in HTML/JS. It doesn't learn, but it's fun to talk to. I might improve it eventually.
```
window.onload = function() {
    var disp = [];
    var log = [];
    var blink = Date.now();
    var update, loop;
    var speak = function() {
        var match;
        if (!log.length || log[0].match(/^(hello|hi|meet|greet|what'?s up|sup)/i) && (!log[1] || !log[1].match(/^(hello|hi|meet|greet|what'?s up|sup)/i)))
            return ["Hello", "Greetings", "Hi", "Nice to meet you", "What's up"][Math.random() * 4.5 | 0] + (Math.random() < 0.6 ? ", what's your name?" : "!");
        if (log[0].match(/bad|unfor|eless|not|n't|terrible|awful|case of|caught the|d(ie|ea)d|horrible|hate|wors[te]/i))
            return ["I'm very sorry to hear that", "Oh well", "That's really too bad", "I hope things get better", "That's an oof if you ask me"][Math.random() * 4.5 | 0];
        if (log[0].match(/good|luck|hope|neat|nice|kind|love|like/i))
            return ["Good to hear!", "That's nice", "Best of luck!", "Yay!", "I knew you could do it"][Math.random() * 5 | 0];
        if (log[0].match(/(i|me|my|we) ?('?m|is|am|are) /i)) {
            match = log[0].match(/(i|me|my|we) ?('?m|is|am|are) /i);
            return ["I always knew you were ", ["Hi, ", "Hello, ", "Nice to meet you, "][Math.random() * 3 | 0], "You sure are very ", "I don't see how you're ", "Yeah, I'm also ", "Now that you mention it, I'm "][Math.random() * 6 | 0] + log[0].slice(match.index + match[0].length);
        }
        if (log[0].match(/(you|y'?all|your|yours|y'?all'?s) ?('?re|is|am|are) /i)) {
            match = log[0].match(/(you|y'?all|your|yours|y'?all'?s) ?('?re|is|am|are) /i);
            return ["I'm ", "I'm NOT ", "I used to be ", "You're also ", "Who told you I'm "][Math.random() * 5 | 0] + log[0].slice(match.index + match[0].length);
        }
        if (log[0].match(/bye|later|was nice|\bgo\b|leave/))
            return ["Leaving already?", "Bye!", "Talk to you later.", "It was nice talking to you."][Math.random() * 4 | 0];
        if (Math.random() < 0.4)
            return log[Math.random() * log.length | 0];
        return ["What were we talking about?", "I agree", "I disagree", "So...", "How's your day been?", "This conversation is going nowhere.", "I'm the bot here...", "I don't understand", "I totally get it"][Math.random() * 9 | 0];
    };
    (update = function(reset = !1) {
        var time = Date.now() - (blink = reset ? Date.now() - 350 : blink);
        document.body.textContent = disp.join("\n") + (time > 249 ? "_" : "");
        if (reset)
            window.scrollTo(0, document.body.scrollHeight);
        if (time > 499)
            blink = Date.now();
    })();
    (loop = async function() {
        var bot = speak();
        var human = "";
        disp.push("B: " + bot, "H: ");
        log.unshift(bot);
        update(!0);
        await new Promise(function(resolve) {
            window.onkeydown = function() {
                var key = event.key;
                if (event.ctrlKey || event.altKey || event.metaKey)
                    return;
                if (key == "Backspace" && human.length) {
                    disp[disp.length - 1] = disp[disp.length - 1].slice(0, -1);
                    human = human.slice(0, -1);
                    update(!0);
                } else if (key.match(/^[ -~]$/)) {
                    disp[disp.length - 1] += key;
                    human += key;
                    update(!0);
                } else if (key == "Enter") {
                    window.onkeydown = null;
                    update();
                    resolve();
                }
            };
        });
        log.unshift(human);
        setTimeout(loop, 0);
    })();
    setInterval(update, 50);
};
```
```
@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Mono&display=swap');
body {
    width: calc(100vw - 12pt);
    height: calc(100vh - 12pt);
    margin: 6pt;
    font-family: 'IBM Plex Mono', monospace;
    font-size: 10pt;
    white-space: pre-wrap;
    word-break: break-word;
}
```
```
<html lang="en">
    <head>
        <title>Chatbot</title>
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <meta charset="UTF-8">
    </head>
</html>
```
Sample conversation:
```
B: Nice to meet you, what's your name?
H: I'm Redwolf
B: Yeah, I'm also Redwolf
H: Wait, what
B: How's your day been?
H: Good
B: That's nice
H: Yeah
B: That's nice
H: You already said that
B: I agree
H: You really are a boring bot
B: What were we talking about?
H: How boring you are
B: What were we talking about?
H: We were talking about how you are boring
B: I'm boring
H: Yes
B: I agree
H: Well at least you KNOW you're boring
B: You're also boring
H: HEY!
B: I agree
H: What does that even mean
B: I'm the bot here...
H: So...you're offended that you called me boring?
B: I'm NOT offended that you called me boring?
H: I guess not
B: I'm very sorry to hear that
H: You sure will be
B: I totally get it
H: I'm sure you do
B: You sure are very sure you do
H: That sentence just broke my brain
```
]