!747
!multi-line strings

m {
  static new L<S> rules;
  static new L<S> statements;
  
  p {
    rules.add([["$1 is the singular of $2." <=> "$2 is the plural of $1."]]);
    statements.add("house is the singular of houses.");
    process();
    print(fromLines(statements));

    ask([[how many plurals does "house" have?]]);
    ask([[what are the plurals of "house"?]]);
  }
  
  static void ask(S q) {
    print("? " + q);
    
    new Map<S, S> map;
    if (match4("how many plurals does $1 have?", q, map))
      print(getPlurals(map.get("$1")).size());
    else if (match4("what are the plurals of $1?", q, map))
      print(structure(getPlurals(map.get("$1"))));
    else
      print("dunno.");
  }
  
  static L<S> getPlurals(S x) {
    S c = "$2 is the plural of " + x;
    print("[" + c + "]");
    MultiMap<S, S> matches = matchAll(c);
    ret matches.get("$2");
  }

  // result of matchStatements ordered by variable
  static MultiMap<S, S> matchAll(S pat) {
    new MultiMap<S, S> map;
    L<Map<S, S>> l = matchStatements(pat);
    print("[" + l.size() + " matches for " + quote(pat) + "]");
    for (Map<S, S> m : l) {
      for (Map.Entry<S, S> e : m.entrySet())
        map.put(e.getKey(), e.getValue());
    }
    ret map;
  }
  
  static void process() {
    for (S rule : rules) {
      new Matches m;
      if (match3("* <=> *", rule, m)) {
        S l = m.unq(0), r = m.unq(1);
        for (Map<S, S> map : matchStatements(l))
          addStatement(convert(r, map));
      }
    }
  }
  
  static L<Map<S, S>> matchStatements(S pat) {
    L<Map<S, S>> l = new ArrayList<Map<S, S>>();
    for (S s : statements) {
      Map<S, S> m = match4(pat, s);
      if (m != null) l.add(m);
    }
    ret l;
  }
  
  static Map<S, S> match4(S pat, S s) {
    new Map<S, S> m;
    ret match4(pat, s, m) ? m : null;
  }
  
  static boolean match4(S pat, S s, Map<S, S> m) {
    L<S> tok1 = parse3(pat), tok2 = parse3(s);
    if (tok1.size() != tok2.size()) ret false;
    m.clear();
    for (int i = 1; i < tok1.size(); i += 2) {
      S t1 = tok1.get(i), t2 = tok2.get(i);
      if (isVar(t1))
        m.put(t1, t2);
      else if (!tokEq(t1, t2))
        ret false;
    }
    ret true;
  }
  
  static boolean tokEq(S a, S b) {
    a = unquote(a);
    b = unquote(b);
    ret a.equalsIgnoreCase(b);
  }
  
  static boolean isVar(S s) {
    ret s.startsWith("$") && s.length() > 1;
  }
  
  static S convert(S r, Map<S, S> matches) {
    L<S> tok = javaTokPlusPeriod(r);
    for (int i = 1; i < tok.size(); i += 2) {
      if (tok.get(i).startsWith("$")) {
        S m = matches.get(tok.get(i));
        if (m != null)
          tok.set(i, m);
      }
    }
    ret join(tok);
  }
  
  static void addStatement(S s) {
    for (S st : statements)
      if (match3(st, s))
        ret;
    statements.add(s);
  }
  
  !include #2000515 // unquote
  !include #1001497 // parseBoolean
  !include #1000709 // formatSnippetID
  
  !include #1001296 // MultiMap
}