[jackhill/mal.git] / dart / stepA_mal.dart

import 'dart:io';

import 'core.dart';
import 'env.dart';
import 'printer.dart' as printer;
import 'reader.dart' as reader;
import 'types.dart';

final Env replEnv = new Env();

void setupEnv(List<String> argv) {
  ns.forEach((sym, fun) => replEnv.set(sym, fun));

  replEnv.set(new MalSymbol('eval'),
      new MalBuiltin((List<MalType> args) => EVAL(args.single, replEnv)));

  replEnv.set(new MalSymbol('*ARGV*'),
      new MalList(argv.map((s) => new MalString(s)).toList()));

  replEnv.set(new MalSymbol('*host-language*'), new MalString('dart'));

  rep('(def! not (fn* (a) (if a false true)))');
  rep("(def! load-file "
      "  (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))");
  rep("(defmacro! cond "
      "  (fn* (& xs) (if (> (count xs) 0) "
      "    (list 'if (first xs) "
      "      (if (> (count xs) 1) "
      "          (nth xs 1) "
      "          (throw \"odd number of forms to cond\")) "
      "      (cons 'cond (rest (rest xs)))))))");
  rep("(def! inc (fn* [x] (+ x 1)))");
  rep("(def! gensym"
      "  (let* [counter (atom 0)]"
      "    (fn* []"
      "      (symbol (str \"G__\" (swap! counter inc))))))");
  rep("(defmacro! or "
      "  (fn* (& xs) "
      "    (if (empty? xs) "
      "        nil "
      "        (if (= 1 (count xs)) "
      "            (first xs) "
      "            (let* (condvar (gensym)) "
      "              `(let* (~condvar ~(first xs)) "
      "                 (if ~condvar ~condvar (or ~@(rest xs)))))))))");
}

/// Returns `true` if [ast] is a macro call.
///
/// This checks that [ast] is a list whose first element is a symbol that refers
/// to a function in the current [env] that is a macro.
bool isMacroCall(MalType ast, Env env) {
  if (ast is MalList) {
    if (ast.isNotEmpty && ast.first is MalSymbol) {
      try {
        var value = env.get(ast.first);
        if (value is MalCallable) {
          return value.isMacro;
        }
      } on NotFoundException {
        return false;
      }
    }
  }
  return false;
}

MalType macroexpand(MalType ast, Env env) {
  while (isMacroCall(ast, env)) {
    var macroSymbol = (ast as MalList).first;
    var macro = env.get(macroSymbol) as MalCallable;
    ast = macro((ast as MalList).sublist(1));
  }
  return ast;
}

MalType quasiquote(MalType ast) {
  bool isPair(MalType ast) {
    return ast is MalIterable && ast.isNotEmpty;
  }

  if (!isPair(ast)) {
    return new MalList([new MalSymbol("quote"), ast]);
  } else {
    var list = ast as MalIterable;
    if (list.first == new MalSymbol("unquote")) {
      return list[1];
    } else if (isPair(list.first) &&
        (list.first as MalIterable).first == new MalSymbol("splice-unquote")) {
      return new MalList([
        new MalSymbol("concat"),
        (list.first as MalIterable)[1],
        quasiquote(new MalList(list.sublist(1)))
      ]);
    } else {
      return new MalList([
        new MalSymbol("cons"),
        quasiquote(list[0]),
        quasiquote(new MalList(list.sublist(1)))
      ]);
    }
  }
}

MalType READ(String x) => reader.read_str(x);

MalType eval_ast(MalType ast, Env env) {
  if (ast is MalSymbol) {
    return env.get(ast);
  } else if (ast is MalList) {
    return new MalList(ast.elements.map((x) => EVAL(x, env)).toList());
  } else if (ast is MalVector) {
    return new MalVector(ast.elements.map((x) => EVAL(x, env)).toList());
  } else if (ast is MalHashMap) {
    var newMap = new Map<MalType, MalType>.from(ast.value);
    for (var key in newMap.keys) {
      newMap[key] = EVAL(newMap[key], env);
    }
    return new MalHashMap(newMap);
  } else {
    return ast;
  }
}

MalType EVAL(MalType ast, Env env) {
  while (true) {
    if (ast is! MalList) {
      return eval_ast(ast, env);
    } else {
      if ((ast as MalList).elements.isEmpty) {
        return ast;
      } else {
        ast = macroexpand(ast, env);
        if (ast is! MalList) return eval_ast(ast, env);
        if ((ast as MalList).isEmpty) return ast;

        var list = ast as MalList;

        if (list.elements.first is MalSymbol) {
          var symbol = list.elements.first as MalSymbol;
          var args = list.elements.sublist(1);
          if (symbol.value == "def!") {
            MalSymbol key = args.first;
            MalType value = EVAL(args[1], env);
            env.set(key, value);
            return value;
          } else if (symbol.value == "defmacro!") {
            MalSymbol key = args.first;
            MalClosure macro = EVAL(args[1], env) as MalClosure;
            macro.isMacro = true;
            env.set(key, macro);
            return macro;
          } else if (symbol.value == "let*") {
            // TODO(het): If elements.length is not even, give helpful error
            Iterable<List<MalType>> pairs(List<MalType> elements) sync* {
              for (var i = 0; i < elements.length; i += 2) {
                yield [elements[i], elements[i + 1]];
              }
            }

            var newEnv = new Env(env);
            MalIterable bindings = args.first;
            for (var pair in pairs(bindings.elements)) {
              MalSymbol key = pair[0];
              MalType value = EVAL(pair[1], newEnv);
              newEnv.set(key, value);
            }
            ast = args[1];
            env = newEnv;
            continue;
          } else if (symbol.value == "do") {
            eval_ast(new MalList(args.sublist(0, args.length - 1)), env);
            ast = args.last;
            continue;
          } else if (symbol.value == "if") {
            var condition = EVAL(args[0], env);
            if (condition is MalNil ||
                condition is MalBool && condition.value == false) {
              // False side of branch
              if (args.length < 3) {
                return new MalNil();
              }
              ast = args[2];
              continue;
            } else {
              // True side of branch
              ast = args[1];
              continue;
            }
          } else if (symbol.value == "fn*") {
            var params = (args[0] as MalIterable)
                .elements
                .map((e) => e as MalSymbol)
                .toList();
            return new MalClosure(
                params,
                args[1],
                env,
                (List<MalType> funcArgs) =>
                    EVAL(args[1], new Env(env, params, funcArgs)));
          } else if (symbol.value == "quote") {
            return args.single;
          } else if (symbol.value == "quasiquote") {
            ast = quasiquote(args.first);
            continue;
          } else if (symbol.value == 'macroexpand') {
            ast = macroexpand(args.first, env);
            continue;
          } else if (symbol.value == 'try*') {
            var body = args.first;
            if (args.length < 2) {
                ast = EVAL(body, env);
                continue;
            }
            var catchClause = args[1] as MalList;
            try {
              ast = EVAL(body, env);
            } catch (e) {
              assert((catchClause.first as MalSymbol).value == 'catch*');
              var exceptionSymbol = catchClause[1] as MalSymbol;
              var catchBody = catchClause[2];
              MalType exceptionValue;
              if (e is MalException) {
                exceptionValue = e.value;
              } else {
                exceptionValue = new MalString(e.toString());
              }
              var newEnv = new Env(env, [exceptionSymbol], [exceptionValue]);
              ast = EVAL(catchBody, newEnv);
            }
            continue;
          }
        }
        var newAst = eval_ast(ast, env) as MalList;
        var f = newAst.elements.first;
        var args = newAst.elements.sublist(1);
        if (f is MalBuiltin) {
          return f.call(args);
        } else if (f is MalClosure) {
          ast = f.ast;
          env = new Env(f.env, f.params, args);
          continue;
        } else {
          throw 'bad!';
        }
      }
    }
  }
}

String PRINT(MalType x) => printer.pr_str(x);

String rep(String x) {
  return PRINT(EVAL(READ(x), replEnv));
}

const prompt = 'user> ';
main(List<String> args) {
  setupEnv(args.isEmpty ? const <String>[] : args.sublist(1));
  if (args.isNotEmpty) {
    rep("(load-file \"${args.first}\")");
    return;
  }
  rep("(println (str \"Mal [\" *host-language* \"]\"))");
  while (true) {
    stdout.write(prompt);
    var input = stdin.readLineSync();
    if (input == null) return;
    var output;
    try {
      output = rep(input);
    } on reader.ParseException catch (e) {
      stdout.writeln("Error: '${e.message}'");
      continue;
    } on NotFoundException catch (e) {
      stdout.writeln("Error: '${e.value}' not found");
      continue;
    } on MalException catch (e) {
      stdout.writeln("Error: ${printer.pr_str(e.value)}");
      continue;
    } on reader.NoInputException {
      continue;
    }
    stdout.writeln(output);
  }
}
Commit	Line	Data
3934e3f8 HT	1	import 'dart:io';
	2
	3	import 'core.dart';
	4	import 'env.dart';
	5	import 'printer.dart' as printer;
	6	import 'reader.dart' as reader;
	7	import 'types.dart';
	8
	9	final Env replEnv = new Env();
	10
	11	void setupEnv(List<String> argv) {
	12	ns.forEach((sym, fun) => replEnv.set(sym, fun));
	13
	14	replEnv.set(new MalSymbol('eval'),
	15	new MalBuiltin((List<MalType> args) => EVAL(args.single, replEnv)));
	16
	17	replEnv.set(new MalSymbol('ARGV'),
	18	new MalList(argv.map((s) => new MalString(s)).toList()));
	19
	20	replEnv.set(new MalSymbol('host-language'), new MalString('dart'));
	21
	22	rep('(def! not (fn* (a) (if a false true)))');
	23	rep("(def! load-file "
	24	" (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))");
	25	rep("(defmacro! cond "
	26	" (fn* (& xs) (if (> (count xs) 0) "
	27	" (list 'if (first xs) "
	28	" (if (> (count xs) 1) "
	29	" (nth xs 1) "
	30	" (throw \"odd number of forms to cond\")) "
	31	" (cons 'cond (rest (rest xs)))))))");
14ab099c NB	32	rep("(def! inc (fn* [x] (+ x 1)))");
	33	rep("(def! gensym"
	34	" (let* [counter (atom 0)]"
	35	" (fn* []"
	36	" (symbol (str \"G__\" (swap! counter inc))))))");
3934e3f8 HT	37	rep("(defmacro! or "
	38	" (fn* (& xs) "
	39	" (if (empty? xs) "
	40	" nil "
	41	" (if (= 1 (count xs)) "
	42	" (first xs) "
	43	" (let* (condvar (gensym)) "
	44	" `(let* (~condvar ~(first xs)) "
	45	" (if ~condvar ~condvar (or ~@(rest xs)))))))))");
	46	}
	47
	48	/// Returns `true` if [ast] is a macro call.
	49	///
	50	/// This checks that [ast] is a list whose first element is a symbol that refers
	51	/// to a function in the current [env] that is a macro.
	52	bool isMacroCall(MalType ast, Env env) {
	53	if (ast is MalList) {
	54	if (ast.isNotEmpty && ast.first is MalSymbol) {
	55	try {
	56	var value = env.get(ast.first);
	57	if (value is MalCallable) {
	58	return value.isMacro;
	59	}
	60	} on NotFoundException {
	61	return false;
	62	}
	63	}
	64	}
	65	return false;
	66	}
	67
	68	MalType macroexpand(MalType ast, Env env) {
	69	while (isMacroCall(ast, env)) {
	70	var macroSymbol = (ast as MalList).first;
	71	var macro = env.get(macroSymbol) as MalCallable;
	72	ast = macro((ast as MalList).sublist(1));
	73	}
	74	return ast;
	75	}
	76
	77	MalType quasiquote(MalType ast) {
	78	bool isPair(MalType ast) {
	79	return ast is MalIterable && ast.isNotEmpty;
	80	}
	81
	82	if (!isPair(ast)) {
	83	return new MalList([new MalSymbol("quote"), ast]);
	84	} else {
	85	var list = ast as MalIterable;
	86	if (list.first == new MalSymbol("unquote")) {
	87	return list[1];
	88	} else if (isPair(list.first) &&
	89	(list.first as MalIterable).first == new MalSymbol("splice-unquote")) {
	90	return new MalList([
	91	new MalSymbol("concat"),
	92	(list.first as MalIterable)[1],
	93	quasiquote(new MalList(list.sublist(1)))
	94	]);
	95	} else {
	96	return new MalList([
	97	new MalSymbol("cons"),
	98	quasiquote(list[0]),
	99	quasiquote(new MalList(list.sublist(1)))
	100	]);
101	}
102	}
103	}
104
105	MalType READ(String x) => reader.read_str(x);
106
107	MalType eval_ast(MalType ast, Env env) {
108	if (ast is MalSymbol) {
109	return env.get(ast);
110	} else if (ast is MalList) {
111	return new MalList(ast.elements.map((x) => EVAL(x, env)).toList());
112	} else if (ast is MalVector) {
113	return new MalVector(ast.elements.map((x) => EVAL(x, env)).toList());
114	} else if (ast is MalHashMap) {
115	var newMap = new Map<MalType, MalType>.from(ast.value);
116	for (var key in newMap.keys) {
117	newMap[key] = EVAL(newMap[key], env);
118	}
119	return new MalHashMap(newMap);
120	} else {
121	return ast;
122	}
123	}
124
125	MalType EVAL(MalType ast, Env env) {
126	while (true) {
127	if (ast is! MalList) {
128	return eval_ast(ast, env);
129	} else {
130	if ((ast as MalList).elements.isEmpty) {
131	return ast;
132	} else {
133	ast = macroexpand(ast, env);
134	if (ast is! MalList) return eval_ast(ast, env);
135	if ((ast as MalList).isEmpty) return ast;
136
137	var list = ast as MalList;
138
139	if (list.elements.first is MalSymbol) {
140	var symbol = list.elements.first as MalSymbol;
141	var args = list.elements.sublist(1);
142	if (symbol.value == "def!") {
143	MalSymbol key = args.first;
144	MalType value = EVAL(args[1], env);
145	env.set(key, value);
146	return value;
147	} else if (symbol.value == "defmacro!") {
148	MalSymbol key = args.first;
149	MalClosure macro = EVAL(args[1], env) as MalClosure;
150	macro.isMacro = true;
151	env.set(key, macro);
152	return macro;
153	} else if (symbol.value == "let*") {
154	// TODO(het): If elements.length is not even, give helpful error
155	Iterable<List<MalType>> pairs(List<MalType> elements) sync* {
156	for (var i = 0; i < elements.length; i += 2) {
157	yield [elements[i], elements[i + 1]];
158	}
159	}
160
161	var newEnv = new Env(env);
162	MalIterable bindings = args.first;
163	for (var pair in pairs(bindings.elements)) {
164	MalSymbol key = pair[0];
165	MalType value = EVAL(pair[1], newEnv);
166	newEnv.set(key, value);
167	}
168	ast = args[1];
169	env = newEnv;
170	continue;
171	} else if (symbol.value == "do") {
172	eval_ast(new MalList(args.sublist(0, args.length - 1)), env);
173	ast = args.last;
174	continue;
175	} else if (symbol.value == "if") {
176	var condition = EVAL(args[0], env);
177	if (condition is MalNil \|\|
178	condition is MalBool && condition.value == false) {
179	// False side of branch
180	if (args.length < 3) {
181	return new MalNil();
182	}
183	ast = args[2];
184	continue;
185	} else {
186	// True side of branch
187	ast = args[1];
188	continue;
189	}
190	} else if (symbol.value == "fn*") {
191	var params = (args[0] as MalIterable)
192	.elements
193	.map((e) => e as MalSymbol)
194	.toList();
195	return new MalClosure(
196	params,
197	args[1],
198	env,
199	(List<MalType> funcArgs) =>
200	EVAL(args[1], new Env(env, params, funcArgs)));
201	} else if (symbol.value == "quote") {
202	return args.single;
203	} else if (symbol.value == "quasiquote") {
204	ast = quasiquote(args.first);
205	continue;
206	} else if (symbol.value == 'macroexpand') {
207	ast = macroexpand(args.first, env);
208	continue;
209	} else if (symbol.value == 'try*') {
210	var body = args.first;
dd7a4f55 JM	211	if (args.length < 2) {
	212	ast = EVAL(body, env);
	213	continue;
	214	}
3934e3f8 HT	215	var catchClause = args[1] as MalList;
	216	try {
	217	ast = EVAL(body, env);
	218	} catch (e) {
	219	assert((catchClause.first as MalSymbol).value == 'catch*');
	220	var exceptionSymbol = catchClause[1] as MalSymbol;
	221	var catchBody = catchClause[2];
	222	MalType exceptionValue;
	223	if (e is MalException) {
	224	exceptionValue = e.value;
	225	} else {
	226	exceptionValue = new MalString(e.toString());
	227	}
	228	var newEnv = new Env(env, [exceptionSymbol], [exceptionValue]);
	229	ast = EVAL(catchBody, newEnv);
	230	}
	231	continue;
	232	}
	233	}
	234	var newAst = eval_ast(ast, env) as MalList;
	235	var f = newAst.elements.first;
	236	var args = newAst.elements.sublist(1);
	237	if (f is MalBuiltin) {
	238	return f.call(args);
	239	} else if (f is MalClosure) {
	240	ast = f.ast;
	241	env = new Env(f.env, f.params, args);
	242	continue;
	243	} else {
	244	throw 'bad!';
	245	}
	246	}
	247	}
	248	}
	249	}
	250
	251	String PRINT(MalType x) => printer.pr_str(x);
	252
	253	String rep(String x) {
dd7a4f55	254	return PRINT(EVAL(READ(x), replEnv));
3934e3f8 HT	255	}
	256
	257	const prompt = 'user> ';
	258	main(List<String> args) {
	259	setupEnv(args.isEmpty ? const <String>[] : args.sublist(1));
	260	if (args.isNotEmpty) {
	261	rep("(load-file \"${args.first}\")");
	262	return;
	263	}
	264	rep("(println (str \"Mal [\" host-language \"]\"))");
	265	while (true) {
	266	stdout.write(prompt);
	267	var input = stdin.readLineSync();
	268	if (input == null) return;
	269	var output;
	270	try {
	271	output = rep(input);
dd7a4f55 JM	272	} on reader.ParseException catch (e) {
	273	stdout.writeln("Error: '${e.message}'");
	274	continue;
	275	} on NotFoundException catch (e) {
	276	stdout.writeln("Error: '${e.value}' not found");
	277	continue;
	278	} on MalException catch (e) {
	279	stdout.writeln("Error: ${printer.pr_str(e.value)}");
	280	continue;
3934e3f8 HT	281	} on reader.NoInputException {
	282	continue;
	283	}
	284	stdout.writeln(output);
	285	}
	286	}