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!752 !include #1002825 // new structure static class Prolog { int varCount; boolean showStuff; class Var extends Lisp { Lisp instance; *() { this("V" + (++varCount)); } *(S name) { super(name); instance = this; } void reset() { instance = this; } public String toString() { if (instance == this) ret getName(); ret instance.toString(); } S getName() { ret head; } } class Clause { Lisp head; Goal body; *(Lisp *head, Goal *body) {} *(Lisp *head) {} Clause copy() { return new Clause(copy2(head), body == null ? null : body.copy()); } public String toString() { //ret head + " :- " + (body == null ? "true" : body); ret body == null ? head.toString() : head + " :- " + body; } }; static class Program { Clause pcar; Program pcdr; *(Clause *pcar, Program *pcdr) {} *(L<Clause> clauses) { this(clauses, 0); } *(L<Clause> clauses, int i) { pcar = clauses.get(i); if (i+1 < l(clauses)) pcdr = new Program(clauses, i+1); } *(Clause... clauses) { this(asList(clauses)); } public String toString() { ret pcdr == null ? pcar + "." : pcar + ".\n" + pcdr; } } class Trail { Var tcar; Trail tcdr; *(Var *tcar, Trail *tcdr) {} } Trail sofar = null; Trail Trail_Note() { return sofar; } void Trail_Push(Var x) { sofar = new Trail(x, sofar); } void Trail_Undo(Trail whereto) { for (; sofar != whereto; sofar = sofar.tcdr) sofar.tcar.reset(); } static class TermVarMapping { new L<Var> vars; *(L<Var> *vars) {} *(Var... vars) { this.vars.addAll(asList(vars)); } void showanswer() { print("TRUE."); for (Var v : vars) print(" " + v.getName() + " = " + v); } } class Goal { Lisp car; Goal cdr; *(Lisp *car, Goal *cdr) {} *(Lisp *car) {} public String toString() { ret cdr == null ? car.toString() : car + "; " + cdr; } void solve(Program p, int level, TermVarMapping map) { if (showStuff) print(indent(level) + "solve@" + level + ": " + this); for (Program q = p; q != null; q = q.pcdr) { Trail t = Trail_Note(); Clause c = q.pcar.copy(); Trail_Undo(t); if (showStuff) print(indent(level) + " try:" + c); if (unify(car, c.head)) { Goal gdash = c.body == null ? cdr : c.body.append(cdr); if (gdash == null) map.showanswer(); else gdash.solve(p, level+1, map); } else if (showStuff) print(indent(level) + " nomatch."); Trail_Undo(t); } } Goal copy() { return new Goal(copy2(car), cdr == null ? null : cdr.copy()); } Goal append(Goal l) { return new Goal(car, cdr == null ? null : cdr.append(l)); } } // class Goal boolean unify(Lisp thiz, Lisp t) { if (thiz instanceof Var) { // TermVar::unify Var v = cast thiz; if (v.instance != v) return unify(v.instance, t); Trail_Push(v); v.instance = t; return true; } // TermCons::unify return unify2(t, thiz); } boolean unify2(Lisp thiz, Lisp t) { if (thiz instanceof Var) return unify(thiz, t); int arity = thiz.size(); if (neq(thiz.head, t.head) || arity != t.size()) return false; for (int i = 0; i < arity; i++) if (!unify(thiz.get(i), t.get(i))) return false; return true; } Lisp copy(Lisp thiz) { if (thiz instanceof Var) { Var v = cast thiz; if (v.instance == v) { Trail_Push(v); v.instance = new Var(); } return v.instance; } ret copy2(thiz); } Lisp newTermCons(Lisp t) { Lisp l = new Lisp(t.head); for (Lisp arg : t) l.add(copy(arg)); ret l; } Lisp copy2(Lisp thiz) { return newTermCons(thiz); } Var newVar() { ret new Var; } Var newVar(S name) { ret new Var(name); } Clause clause(Lisp head, Goal body) { ret prologify(new Clause(head, body)); } Clause clause(Lisp head) { ret prologify(new Clause(head)); } Clause clause(Lisp head, Lisp body) { ret clause(head, new Goal(body)); } Lisp prologify(Lisp term) { ret prologify(term, new HashMap); } Clause prologify(Clause c) { new HashMap vars; ret new Clause( prologify(c.head, vars), prologify(c.body, vars)); } Goal prologify(Goal goal, Map<S, Var> vars) { if (goal == null) ret null; ret new Goal( prologify(goal.car, vars), prologify(goal.cdr, vars)); } Lisp prologify(Lisp term, Map<S, Var> vars) { if (term == null) ret null; if (snlIsVar(term)) { Var v = vars.get(term.head); if (v == null) vars.put(term.head, v = newVar(term.head)); ret v; } else { Lisp l = new Lisp(term.head); for (Lisp arg : term) l.add(prologify(arg, vars)); ret l; } } L<Var> findVars(Lisp term) { new IdentityHashMap<Var, Boolean> map; findVars(term, map); ret asList(map.keySet()); } void findVars(Lisp term, IdentityHashMap<Var, Boolean> map) { if (term instanceof Var) map.put((Var) term, Boolean.TRUE); else for (Lisp arg : term) findVars(arg, map); } static Map<S, Var> makeVarMap(L<Var> vars) { new HashMap<S, Var> map; for (Var v : vars) map.put(v.getName(), v); ret map; } // Executor stack entry static class Entry { Goal goal; Program q; Trail trail; boolean trailSet; *(Program *q, Goal *goal) {} } Executor executor; Executor newExecutor(Program p, Goal goal) { if (executor != null) fail("Already got an executor"); ret executor = new Executor(p, goal); } // a stackless, step-based executor for Prolog queries // only one instance per Prolog instance! class Executor { Program p; new L<Entry> stack; *(Program *p, Goal goal) { stack.add(new Entry(p, goal)); } int level() { ret l(stack)-1; } boolean done() { ret empty(stack); } boolean step() { if (done()) fail("done!"); // safety Entry e = last(stack); if (e.trailSet) { Trail_Undo(e.trail); e.trailSet = false; } if (e.q == null) { // program loop ends removeLast(stack); ret false; } if (showStuff) print(indent(level()) + "solve@" + level() + ": " + e.goal); // now in program loop e.trail = Trail_Note(); e.trailSet = true; Clause c = e.q.pcar.copy(); e.q = e.q.pcdr; // next clause in program Trail_Undo(e.trail); if (showStuff) print(indent(level()) + " try:" + c); if (unify(e.goal.car, c.head)) { Goal gdash = c.body == null ? e.goal.cdr : c.body.append(e.goal.cdr); if (gdash == null) ret true; else { stack.add(new Entry(p, gdash)); ret false; } } else if (showStuff) print(indent(level()) + " nomatch."); ret false; } } } // class Prolog p { new Prolog p; /* A sample test program: append */ S at_app = "app"; S at_cons = "cons"; Lisp f_nil = lisp("nil"); Lisp f_1 = lisp("1"); Lisp f_2 = lisp("2"); Lisp f_3 = lisp("3"); // Try making a clause from pure Lisp Lisp lhs1 = lisp("app", "nil", "X", "X"); Prolog.Clause c1 = p.clause(lhs1); print("c1: " + structure_seen(c1)); Lisp rhs2 = lisp(at_app, "L", "M", "N"); Lisp lhs2 = lisp(at_app, lisp(at_cons, "X", "L"), "M", lisp(at_cons, "X", "N")); Prolog.Clause c2 = p.clause(lhs2, rhs2); // Test prologify Lisp rhs3pre = lisp("app", "I", "J", lisp("cons", "1", lisp("cons", "2", lisp("cons", "3", "nil")))); Lisp rhs3 = p.prologify(rhs3pre); L<Prolog.Var> vars = p.findVars(rhs3); print("Vars: " + structure_seen(vars)); Map<S, Prolog.Var> varMap = Prolog.makeVarMap(vars); Prolog.Var v_i = varMap.get("I"); Prolog.Var v_j = varMap.get("J"); assertNotNull(v_i); assertNotNull(v_j); Prolog.Goal g1 = p.new Goal(rhs3); Prolog.Program test_p = new Prolog.Program(c1, c2); Prolog.Program test_p2 = new Prolog.Program(c2, c1); Prolog.TermVarMapping var_name_map = new Prolog.TermVarMapping(v_i, v_j); /* print("=======Append with normal clause order:"); print(test_p); print(); g1.solve(test_p, 0, var_name_map); print(); print("=======Append with reversed normal clause order:"); print(test_p2); print(); g1.solve(test_p2, 0, var_name_map); */ p.showStuff = true; Prolog.Executor e = p.newExecutor(test_p, g1); int safety = 0; while (!e.done() && ++safety < 1000) { if (e.step()) { print("Solution at iteration " + safety + ":"); var_name_map.showanswer(); } } print("Steps: " + safety); }
Began life as a copy of #1002820
download show line numbers debug dex old transpilations
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Snippet ID: | #1002823 |
Snippet name: | Prolog Interpreter (with executor, developing) |
Eternal ID of this version: | #1002823/1 |
Text MD5: | 4be912e0b0bb18aa752807baab4f4ffa |
Transpilation MD5: | da2062398da412689a5d19828683380d |
Author: | stefan |
Category: | javax |
Type: | JavaX source code |
Public (visible to everyone): | Yes |
Archived (hidden from active list): | No |
Created/modified: | 2016-02-29 01:08:30 |
Source code size: | 9732 bytes / 422 lines |
Pitched / IR pitched: | No / No |
Views / Downloads: | 982 / 1022 |
Referenced in: | [show references] |