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