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2539e6af KR |
1 | //****************************************************************************** |
2 | // MAL - step 8 - macros | |
3 | //****************************************************************************** | |
4 | // This file is automatically generated from templates/step.swift. Rather than | |
5 | // editing it directly, it's probably better to edit templates/step.swift and | |
6 | // regenerate this file. Otherwise, your change might be lost if/when someone | |
7 | // else performs that process. | |
8 | //****************************************************************************** | |
9 | ||
10 | import Foundation | |
11 | ||
12 | // The number of times EVAL has been entered recursively. We keep track of this | |
13 | // so that we can protect against overrunning the stack. | |
14 | // | |
15 | var EVAL_level = 0 | |
16 | ||
17 | // The maximum number of times we let EVAL recurse before throwing an exception. | |
18 | // Testing puts this at some place between 1800 and 1900. Let's keep it at 500 | |
19 | // for safety's sake. | |
20 | // | |
21 | let EVAL_leval_max = 500 | |
22 | ||
23 | // Control whether or not tail-call optimization (TCO) is enabled. We want it | |
24 | // `true` most of the time, but may disable it for debugging purposes (it's | |
25 | // easier to get a meaningful backtrace that way). | |
26 | // | |
27 | let TCO = true | |
28 | ||
29 | // Control whether or not we emit debugging statements in EVAL. | |
30 | // | |
31 | let DEBUG_EVAL = false | |
32 | ||
b3ec2290 KR |
33 | // String used to prefix information logged in EVAL. Increasing lengths of the |
34 | // string are used the more EVAL is recursed. | |
35 | // | |
2539e6af KR |
36 | let INDENT_TEMPLATE = "|----|----|----|----|----|----|----|----|" + |
37 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
38 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
39 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
40 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
41 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
42 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
43 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
44 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
45 | "----|----|----|----|----|----|----|----|----|----|----|" + | |
46 | "----|----|----|----|----|----|----|----|----|----|----|" | |
b3ec2290 KR |
47 | |
48 | // Holds the prefix of INDENT_TEMPLATE used for actual logging. | |
49 | // | |
2c4b8bd1 | 50 | var indent = String() |
2539e6af | 51 | |
b3ec2290 KR |
52 | // Symbols used in this module. |
53 | // | |
2539e6af KR |
54 | let kSymbolArgv = MalSymbol(symbol: "*ARGV*") |
55 | let kSymbolConcat = MalSymbol(symbol: "concat") | |
56 | let kSymbolCons = MalSymbol(symbol: "cons") | |
57 | let kSymbolDef = MalSymbol(symbol: "def!") | |
58 | let kSymbolDefMacro = MalSymbol(symbol: "defmacro!") | |
59 | let kSymbolDo = MalSymbol(symbol: "do") | |
60 | let kSymbolEval = MalSymbol(symbol: "eval") | |
b3ec2290 | 61 | let kSymbolFn = MalSymbol(symbol: "fn*") |
2539e6af KR |
62 | let kSymbolIf = MalSymbol(symbol: "if") |
63 | let kSymbolLet = MalSymbol(symbol: "let*") | |
64 | let kSymbolMacroExpand = MalSymbol(symbol: "macroexpand") | |
b3ec2290 | 65 | let kSymbolQuasiQuote = MalSymbol(symbol: "quasiquote") |
2539e6af KR |
66 | let kSymbolQuote = MalSymbol(symbol: "quote") |
67 | let kSymbolSpliceUnquote = MalSymbol(symbol: "splice-unquote") | |
68 | let kSymbolUnquote = MalSymbol(symbol: "unquote") | |
69 | ||
70 | // Class to help control the incrementing and decrementing of EVAL_level. We | |
71 | // create one of these on entry to EVAL, incrementing the level. When the | |
72 | // variable goes out of scope, the object is destroyed, decrementing the level. | |
73 | // | |
74 | class EVAL_Counter { | |
75 | init() { | |
76 | ++EVAL_level | |
77 | } | |
78 | deinit { | |
79 | --EVAL_level | |
80 | } | |
81 | } | |
82 | ||
83 | // Parse the string into an AST. | |
84 | // | |
85 | func READ(str: String) -> MalVal { | |
86 | return read_str(str) | |
87 | } | |
88 | ||
89 | // Return whether or not `val` is a non-empty list. | |
90 | // | |
91 | func is_pair(val:MalVal) -> Bool { | |
92 | if !is_sequence(val) { return false } | |
1c76df7d | 93 | let list = val as! MalSequence |
2539e6af KR |
94 | return !list.isEmpty |
95 | } | |
96 | ||
97 | // Expand macros for as long as the expression looks like a macro invocation. | |
98 | // | |
99 | func macroexpand(var ast:MalVal, env:Environment) -> MalVal { | |
100 | while true { | |
101 | if !is_list(ast) { break } | |
1c76df7d | 102 | let ast_as_list = ast as! MalList |
2539e6af KR |
103 | if ast_as_list.isEmpty { break } |
104 | let first = ast_as_list.first() | |
105 | if !is_symbol(first) { break } | |
1c76df7d | 106 | let macro_name = first as! MalSymbol |
2539e6af KR |
107 | let obj = env.get(macro_name) |
108 | if obj == nil { break } | |
109 | if !is_closure(obj!) { break } | |
1c76df7d | 110 | let macro = obj! as! MalClosure |
2539e6af KR |
111 | if !macro.is_macro { break } |
112 | var new_env = Environment(outer: macro.env) | |
113 | let rest = ast_as_list.rest() | |
114 | let res = new_env.set_bindings(macro.args, with_exprs:rest) | |
115 | if is_error(res) { return res } | |
116 | ast = EVAL(macro.body, new_env) | |
117 | } | |
118 | return ast | |
119 | } | |
120 | ||
121 | // Evaluate `quasiquote`, possibly recursing in the process. | |
122 | // | |
123 | // As with quote, unquote, and splice-unquote, quasiquote takes a single | |
124 | // parameter, typically a list. In the general case, this list is processed | |
125 | // recursively as: | |
126 | // | |
127 | // (quasiquote (first rest...)) -> (cons (quasiquote first) (quasiquote rest)) | |
128 | // | |
129 | // In the processing of the parameter passed to it, quasiquote handles three | |
130 | // special cases: | |
131 | // | |
132 | // * If the parameter is an atom or an empty list, the following expression | |
133 | // is formed and returned for evaluation: | |
134 | // | |
135 | // (quasiquote atom-or-empty-list) -> (quote atom-or-empty-list) | |
136 | // | |
137 | // * If the first element of the non-empty list is the symbol "unquote" | |
138 | // followed by a second item, the second item is returned as-is: | |
139 | // | |
140 | // (quasiquote (unquote fred)) -> fred | |
141 | // | |
142 | // * If the first element of the non-empty list is another list containing | |
143 | // the symbol "splice-unquote" followed by a list, that list is catenated | |
144 | // with the quasiquoted result of the remaining items in the non-empty | |
145 | // parent list: | |
146 | // | |
147 | // (quasiquote (splice-unquote list) rest...) -> (items-from-list items-from-quasiquote(rest...)) | |
148 | // | |
149 | // Note the inconsistent handling between "quote" and "splice-quote". The former | |
150 | // is handled when this function is handed a list that starts with "quote", | |
151 | // whereas the latter is handled when this function is handled a list whose | |
152 | // first element is a list that starts with "splice-quote". The handling of the | |
153 | // latter is forced by the need to incorporate the results of (splice-quote | |
154 | // list) with the remaining items of the list containing that splice-quote | |
155 | // expression. However, it's not clear to me why the handling of "unquote" is | |
156 | // not handled similarly, for consistency's sake. | |
157 | ||
158 | func quasiquote(qq_arg:MalVal) -> MalVal { | |
159 | ||
160 | // If the argument is an atom or empty list: | |
161 | // | |
162 | // Return: (quote <argument>) | |
163 | ||
164 | if !is_pair(qq_arg) { | |
165 | return MalList(objects: kSymbolQuote, qq_arg) | |
166 | } | |
167 | ||
168 | // The argument is a non-empty list -- that is (item rest...) | |
169 | ||
170 | // If the first item from the list is a symbol and it's "unquote" -- that | |
171 | // is, (unquote item ignored...): | |
172 | // | |
173 | // Return: item | |
174 | ||
1c76df7d | 175 | let qq_list = qq_arg as! MalSequence |
2539e6af | 176 | if is_symbol(qq_list.first()) { |
1c76df7d | 177 | let sym = qq_list.first() as! MalSymbol |
2539e6af KR |
178 | if sym == kSymbolUnquote { |
179 | return qq_list.count >= 2 ? qq_list[1] : MalNil() | |
180 | } | |
181 | } | |
182 | ||
183 | // If the first item from the list is itself a non-empty list starting with | |
184 | // "splice-unquote"-- that is, ((splice-unquote item ignored...) rest...): | |
185 | // | |
186 | // Return: (concat item quasiquote(rest...)) | |
187 | ||
188 | if is_pair(qq_list.first()) { | |
1c76df7d | 189 | let qq_list_item0 = qq_list.first() as! MalSequence |
2539e6af | 190 | if is_symbol(qq_list_item0.first()) { |
1c76df7d | 191 | let sym = qq_list_item0.first() as! MalSymbol |
2539e6af KR |
192 | if sym == kSymbolSpliceUnquote { |
193 | let result = quasiquote(qq_list.rest()) | |
194 | if is_error(result) { return result } | |
195 | return MalList(array: [kSymbolConcat, qq_list_item0[1], result]) | |
196 | } | |
197 | } | |
198 | } | |
199 | ||
200 | // General case: (item rest...): | |
201 | // | |
202 | // Return: (cons (quasiquote item) (quasiquote (rest...)) | |
203 | ||
204 | let first = quasiquote(qq_list.first()) | |
205 | if is_error(first) { return first } | |
206 | ||
207 | let rest = quasiquote(qq_list.rest()) | |
208 | if is_error(rest) { return rest } | |
209 | ||
210 | return MalList(objects: kSymbolCons, first, rest) | |
211 | } | |
212 | ||
213 | // Perform a simple evaluation of the `ast` object. If it's a symbol, | |
214 | // dereference it and return its value. If it's a collection, call EVAL on all | |
215 | // elements (or just the values, in the case of the hashmap). Otherwise, return | |
216 | // the object unchanged. | |
217 | // | |
218 | func eval_ast(ast: MalVal, env: Environment) -> MalVal { | |
3829ee8c KR |
219 | switch ast.type { |
220 | case .TypeSymbol: | |
1c76df7d | 221 | let symbol = ast as! MalSymbol |
3829ee8c KR |
222 | if let val = env.get(symbol) { |
223 | return val | |
224 | } | |
225 | return MalError(message: "'\(symbol)' not found") // Specific text needed to match MAL unit tests | |
226 | case .TypeList: | |
1c76df7d | 227 | let list = ast as! MalList |
3829ee8c KR |
228 | var result = [MalVal]() |
229 | result.reserveCapacity(list.count) | |
230 | for item in list { | |
231 | let eval = EVAL(item, env) | |
232 | if is_error(eval) { return eval } | |
233 | result.append(eval) | |
234 | } | |
235 | return MalList(array: result) | |
236 | case .TypeVector: | |
1c76df7d | 237 | let vec = ast as! MalVector |
3829ee8c KR |
238 | var result = [MalVal]() |
239 | result.reserveCapacity(vec.count) | |
240 | for item in vec { | |
241 | let eval = EVAL(item, env) | |
242 | if is_error(eval) { return eval } | |
243 | result.append(eval) | |
244 | } | |
245 | return MalVector(array: result) | |
246 | case .TypeHashMap: | |
1c76df7d | 247 | let hash = ast as! MalHashMap |
3829ee8c KR |
248 | var result = [MalVal]() |
249 | result.reserveCapacity(hash.count * 2) | |
250 | for (k, v) in hash { | |
251 | let new_v = EVAL(v, env) | |
252 | if is_error(new_v) { return new_v } | |
253 | result.append(k) | |
254 | result.append(new_v) | |
255 | } | |
256 | return MalHashMap(array: result) | |
257 | default: | |
258 | return ast | |
2539e6af | 259 | } |
2539e6af KR |
260 | } |
261 | ||
b3ec2290 KR |
262 | enum TCOVal { |
263 | case NoResult | |
264 | case Return(MalVal) | |
265 | case Continue(MalVal, Environment) | |
266 | ||
267 | init() { self = .NoResult } | |
268 | init(_ result: MalVal) { self = .Return(result) } | |
269 | init(_ ast: MalVal, _ env: Environment) { self = .Continue(ast, env) } | |
270 | init(_ e: String) { self = .Return(MalError(message: e)) } | |
271 | } | |
272 | ||
273 | // EVALuate "def!" and "defmacro!". | |
274 | // | |
275 | func eval_def(list: MalSequence, env: Environment) -> TCOVal { | |
276 | if list.count != 3 { | |
277 | return TCOVal("expected 2 arguments to def!, got \(list.count - 1)") | |
278 | } | |
1c76df7d | 279 | let arg0 = list[0] as! MalSymbol |
b3ec2290 KR |
280 | let arg1 = list[1] |
281 | let arg2 = list[2] | |
282 | if !is_symbol(arg1) { | |
283 | return TCOVal("expected symbol for first argument to def!") | |
284 | } | |
1c76df7d | 285 | let sym = arg1 as! MalSymbol |
b3ec2290 KR |
286 | let value = EVAL(arg2, env) |
287 | if is_error(value) { return TCOVal(value) } | |
288 | if arg0 == kSymbolDefMacro { | |
289 | if is_closure(value) { | |
1c76df7d | 290 | let as_closure = value as! MalClosure |
b3ec2290 KR |
291 | as_closure.is_macro = true |
292 | } else { | |
293 | return TCOVal("expected closure, got \(value)") | |
294 | } | |
295 | } | |
296 | return TCOVal(env.set(sym, value)) | |
297 | } | |
298 | ||
299 | // EVALuate "let*". | |
300 | // | |
301 | func eval_let(list: MalSequence, env: Environment) -> TCOVal { | |
302 | if list.count != 3 { | |
303 | return TCOVal("expected 2 arguments to let*, got \(list.count - 1)") | |
304 | } | |
305 | let arg1 = list[1] | |
306 | let arg2 = list[2] | |
307 | if !is_sequence(arg1) { | |
308 | return TCOVal("expected list for first argument to let*") | |
309 | } | |
1c76df7d | 310 | let bindings = arg1 as! MalSequence |
b3ec2290 KR |
311 | if bindings.count % 2 == 1 { |
312 | return TCOVal("expected even number of elements in bindings to let*, got \(bindings.count)") | |
313 | } | |
314 | var new_env = Environment(outer: env) | |
315 | for var index = 0; index < bindings.count; index += 2 { | |
316 | let binding_name = bindings[index] | |
317 | let binding_value = bindings[index + 1] | |
318 | ||
319 | if !is_symbol(binding_name) { | |
320 | return TCOVal("expected symbol for first element in binding pair") | |
321 | } | |
1c76df7d | 322 | let binding_symbol = binding_name as! MalSymbol |
b3ec2290 KR |
323 | let evaluated_value = EVAL(binding_value, new_env) |
324 | if is_error(evaluated_value) { return TCOVal(evaluated_value) } | |
325 | new_env.set(binding_symbol, evaluated_value) | |
326 | } | |
327 | if TCO { | |
328 | return TCOVal(arg2, new_env) | |
329 | } | |
330 | return TCOVal(EVAL(arg2, new_env)) | |
331 | } | |
332 | ||
333 | // EVALuate "do". | |
334 | // | |
335 | func eval_do(list: MalSequence, env: Environment) -> TCOVal { | |
336 | if TCO { | |
337 | let eval = eval_ast(MalList(slice: list[1..<list.count-1]), env) | |
338 | if is_error(eval) { return TCOVal(eval) } | |
339 | return TCOVal(list.last(), env) | |
340 | } | |
341 | ||
342 | let evaluated_ast = eval_ast(list.rest(), env) | |
343 | if is_error(evaluated_ast) { return TCOVal(evaluated_ast) } | |
1c76df7d | 344 | let evaluated_seq = evaluated_ast as! MalSequence |
b3ec2290 KR |
345 | return TCOVal(evaluated_seq.last()) |
346 | } | |
347 | ||
348 | // EVALuate "if". | |
349 | // | |
350 | func eval_if(list: MalSequence, env: Environment) -> TCOVal { | |
351 | if list.count < 3 { | |
352 | return TCOVal("expected at least 2 arguments to if, got \(list.count - 1)") | |
353 | } | |
354 | let cond_result = EVAL(list[1], env) | |
355 | var new_ast = MalVal() | |
356 | if is_truthy(cond_result) { | |
357 | new_ast = list[2] | |
358 | } else if list.count == 4 { | |
359 | new_ast = list[3] | |
360 | } else { | |
361 | return TCOVal(MalNil()) | |
362 | } | |
363 | if TCO { | |
364 | return TCOVal(new_ast, env) | |
365 | } | |
366 | return TCOVal(EVAL(new_ast, env)) | |
367 | } | |
368 | ||
369 | // EVALuate "fn*". | |
370 | // | |
371 | func eval_fn(list: MalSequence, env: Environment) -> TCOVal { | |
372 | if list.count != 3 { | |
373 | return TCOVal("expected 2 arguments to fn*, got \(list.count - 1)") | |
374 | } | |
375 | if !is_sequence(list[1]) { | |
376 | return TCOVal("expected list or vector for first argument to fn*") | |
377 | } | |
1c76df7d | 378 | return TCOVal(MalClosure(eval: EVAL, args:list[1] as! MalSequence, body:list[2], env:env)) |
b3ec2290 KR |
379 | } |
380 | ||
381 | // EVALuate "quote". | |
382 | // | |
383 | func eval_quote(list: MalSequence, env: Environment) -> TCOVal { | |
384 | if list.count >= 2 { | |
385 | return TCOVal(list[1]) | |
386 | } | |
387 | return TCOVal(MalNil()) | |
388 | } | |
389 | ||
390 | // EVALuate "quasiquote". | |
391 | // | |
392 | func eval_quasiquote(list: MalSequence, env: Environment) -> TCOVal { | |
393 | if list.count >= 2 { | |
394 | if TCO { | |
395 | return TCOVal(quasiquote(list[1]), env) | |
396 | } | |
397 | return TCOVal(EVAL(quasiquote(list[1]), env)) | |
398 | } | |
399 | return TCOVal("Expected non-nil parameter to 'quasiquote'") | |
400 | } | |
401 | ||
402 | // EVALuate "macroexpand". | |
403 | // | |
404 | func eval_macroexpand(list: MalSequence, env: Environment) -> TCOVal { | |
405 | if list.count >= 2 { | |
406 | return TCOVal(macroexpand(list[1], env)) | |
407 | } | |
408 | return TCOVal("Expected parameter to 'macroexpand'") | |
409 | } | |
410 | ||
2539e6af KR |
411 | // Walk the AST and completely evaluate it, handling macro expansions, special |
412 | // forms and function calls. | |
413 | // | |
414 | func EVAL(var ast: MalVal, var env: Environment) -> MalVal { | |
2c4b8bd1 | 415 | let x = EVAL_Counter() |
2539e6af KR |
416 | if EVAL_level > EVAL_leval_max { |
417 | return MalError(message: "Recursing too many levels (> \(EVAL_leval_max))") | |
418 | } | |
419 | ||
2c4b8bd1 KR |
420 | if DEBUG_EVAL { |
421 | indent = prefix(INDENT_TEMPLATE, EVAL_level) | |
422 | } | |
2539e6af KR |
423 | |
424 | while true { | |
425 | if is_error(ast) { return ast } | |
426 | if DEBUG_EVAL { println("\(indent)> \(ast)") } | |
427 | ||
b3ec2290 | 428 | if !is_list(ast) { |
2539e6af | 429 | |
b3ec2290 | 430 | // Not a list -- just evaluate and return. |
2539e6af | 431 | |
b3ec2290 KR |
432 | let answer = eval_ast(ast, env) |
433 | if DEBUG_EVAL { println("\(indent)>>> \(answer)") } | |
434 | return answer | |
435 | } | |
2539e6af | 436 | |
b3ec2290 | 437 | // Special handling if it's a list. |
2539e6af | 438 | |
1c76df7d | 439 | var list = ast as! MalList |
b3ec2290 KR |
440 | ast = macroexpand(ast, env) |
441 | if !is_list(ast) { return ast } | |
1c76df7d | 442 | list = ast as! MalList |
2539e6af | 443 | |
b3ec2290 | 444 | if DEBUG_EVAL { println("\(indent)>. \(list)") } |
2539e6af | 445 | |
b3ec2290 KR |
446 | if list.isEmpty { |
447 | return list | |
448 | } | |
2539e6af | 449 | |
b3ec2290 KR |
450 | // Check for special forms, where we want to check the operation |
451 | // before evaluating all of the parameters. | |
452 | ||
453 | let arg0 = list.first() | |
454 | if is_symbol(arg0) { | |
455 | var res: TCOVal | |
1c76df7d | 456 | let fn_symbol = arg0 as! MalSymbol |
b3ec2290 KR |
457 | |
458 | switch fn_symbol { | |
459 | case kSymbolDef: res = eval_def(list, env) | |
460 | case kSymbolDefMacro: res = eval_def(list, env) | |
461 | case kSymbolLet: res = eval_let(list, env) | |
462 | case kSymbolDo: res = eval_do(list, env) | |
463 | case kSymbolIf: res = eval_if(list, env) | |
464 | case kSymbolFn: res = eval_fn(list, env) | |
465 | case kSymbolQuote: res = eval_quote(list, env) | |
466 | case kSymbolQuasiQuote: res = eval_quasiquote(list, env) | |
467 | case kSymbolMacroExpand: res = eval_macroexpand(list, env) | |
468 | default: res = TCOVal() | |
2539e6af | 469 | } |
b3ec2290 KR |
470 | switch res { |
471 | case let .Return(result): return result | |
472 | case let .Continue(new_ast, new_env): ast = new_ast; env = new_env; continue | |
473 | case .NoResult: break | |
474 | } | |
475 | } | |
2539e6af | 476 | |
b3ec2290 | 477 | // Standard list to be applied. Evaluate all the elements first. |
2539e6af | 478 | |
b3ec2290 KR |
479 | let eval = eval_ast(ast, env) |
480 | if is_error(eval) { return eval } | |
2539e6af | 481 | |
b3ec2290 | 482 | // The result had better be a list and better be non-empty. |
2539e6af | 483 | |
1c76df7d | 484 | let eval_list = eval as! MalList |
b3ec2290 KR |
485 | if eval_list.isEmpty { |
486 | return eval_list | |
487 | } | |
2539e6af | 488 | |
b3ec2290 KR |
489 | if DEBUG_EVAL { println("\(indent)>> \(eval)") } |
490 | ||
491 | // Get the first element of the list and execute it. | |
492 | ||
493 | let first = eval_list.first() | |
494 | let rest = eval_list.rest() | |
495 | ||
496 | if is_builtin(first) { | |
1c76df7d | 497 | let fn = first as! MalBuiltin |
b3ec2290 KR |
498 | let answer = fn.apply(rest) |
499 | if DEBUG_EVAL { println("\(indent)>>> \(answer)") } | |
500 | return answer | |
501 | } else if is_closure(first) { | |
1c76df7d | 502 | let fn = first as! MalClosure |
b3ec2290 KR |
503 | var new_env = Environment(outer: fn.env) |
504 | let result = new_env.set_bindings(fn.args, with_exprs:rest) | |
505 | if is_error(result) { return result } | |
506 | if TCO { | |
507 | env = new_env | |
508 | ast = fn.body | |
509 | continue | |
510 | } | |
511 | let answer = EVAL(fn.body, new_env) | |
512 | if DEBUG_EVAL { println("\(indent)>>> \(answer)") } | |
513 | return answer | |
2539e6af KR |
514 | } |
515 | ||
b3ec2290 KR |
516 | // The first element wasn't a function to be executed. Return an |
517 | // error saying so. | |
2539e6af | 518 | |
b3ec2290 | 519 | return MalError(message: "first list item does not evaluate to a function: \(first)") |
2539e6af KR |
520 | } |
521 | } | |
522 | ||
523 | // Convert the value into a human-readable string for printing. | |
524 | // | |
525 | func PRINT(exp: MalVal) -> String? { | |
526 | if is_error(exp) { return nil } | |
527 | return pr_str(exp, true) | |
528 | } | |
529 | ||
530 | // Perform the READ and EVAL steps. Useful for when you don't care about the | |
531 | // printable result. | |
532 | // | |
533 | func RE(text: String, env: Environment) -> MalVal? { | |
534 | if text.isEmpty { return nil } | |
535 | let ast = READ(text) | |
536 | if is_error(ast) { | |
537 | println("Error parsing input: \(ast)") | |
538 | return nil | |
539 | } | |
540 | let exp = EVAL(ast, env) | |
541 | if is_error(exp) { | |
542 | println("Error evaluating input: \(exp)") | |
543 | return nil | |
544 | } | |
545 | return exp | |
546 | } | |
547 | ||
548 | // Perform the full READ/EVAL/PRINT, returning a printable string. | |
549 | // | |
550 | func REP(text: String, env: Environment) -> String? { | |
551 | let exp = RE(text, env) | |
552 | if exp == nil { return nil } | |
553 | return PRINT(exp!) | |
554 | } | |
555 | ||
556 | // Perform the full REPL. | |
557 | // | |
558 | func REPL(env: Environment) { | |
559 | while true { | |
560 | if let text = _readline("user> ") { | |
561 | if let output = REP(text, env) { | |
562 | println("\(output)") | |
563 | } | |
564 | } else { | |
565 | println() | |
566 | break | |
567 | } | |
568 | } | |
569 | } | |
570 | ||
571 | // Process any command line arguments. Any trailing arguments are incorporated | |
572 | // into the environment. Any argument immediately after the process name is | |
573 | // taken as a script to execute. If one exists, it is executed in lieu of | |
574 | // running the REPL. | |
575 | // | |
576 | func process_command_line(args:[String], env:Environment) -> Bool { | |
577 | var argv = MalList() | |
578 | if args.count > 2 { | |
579 | let args1 = args[2..<args.count] | |
580 | let args2 = args1.map { MalString(unescaped: $0) as MalVal } | |
581 | let args3 = [MalVal](args2) | |
582 | argv = MalList(array: args3) | |
583 | } | |
584 | env.set(kSymbolArgv, argv) | |
585 | ||
586 | if args.count > 1 { | |
587 | RE("(load-file \"\(args[1])\")", env) | |
588 | return false | |
589 | } | |
590 | ||
591 | return true | |
592 | } | |
593 | ||
594 | func main() { | |
595 | var env = Environment(outer: nil) | |
596 | ||
597 | load_history_file() | |
598 | load_builtins(env) | |
599 | ||
600 | RE("(def! not (fn* (a) (if a false true)))", env) | |
601 | RE("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))", env) | |
602 | RE("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) " + | |
603 | "(throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))", env) | |
604 | RE("(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) " + | |
605 | "`(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))", env) | |
606 | ||
607 | env.set(kSymbolEval, MalBuiltin(function: { | |
608 | unwrap($0) { | |
609 | (ast:MalVal) -> MalVal in | |
610 | EVAL(ast, env) | |
611 | } | |
612 | })) | |
613 | ||
614 | if process_command_line(Process.arguments, env) { | |
615 | REPL(env) | |
616 | } | |
617 | ||
618 | save_history_file() | |
619 | } |