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9ddacf86 KN |
1 | ;"mwexpand.scm" macro expander |
2 | ; Copyright 1992 William Clinger | |
3 | ; | |
4 | ; Permission to copy this software, in whole or in part, to use this | |
5 | ; software for any lawful purpose, and to redistribute this software | |
6 | ; is granted subject to the restriction that all copies made of this | |
7 | ; software must include this copyright notice in full. | |
8 | ; | |
9 | ; I also request that you send me a copy of any improvements that you | |
10 | ; make to this software so that they may be incorporated within it to | |
11 | ; the benefit of the Scheme community. | |
12 | ||
13 | ; The external entry points and kernel of the macro expander. | |
14 | ; | |
15 | ; Part of this code is snarfed from the Twobit macro expander. | |
16 | ||
17 | (define mw:define-syntax-scope | |
18 | (let ((flag 'letrec)) | |
19 | (lambda args | |
20 | (cond ((null? args) flag) | |
21 | ((not (null? (cdr args))) | |
22 | (apply mw:warn | |
23 | "Too many arguments passed to define-syntax-scope" | |
24 | args)) | |
25 | ((memq (car args) '(letrec letrec* let*)) | |
26 | (set! flag (car args))) | |
27 | (else (mw:warn "Unrecognized argument to define-syntax-scope" | |
28 | (car args))))))) | |
29 | ||
30 | (define mw:quit ; assigned by macwork:expand | |
31 | (lambda (v) v)) | |
32 | ||
33 | (define (macwork:expand def-or-exp) | |
34 | (call-with-current-continuation | |
35 | (lambda (k) | |
36 | (set! mw:quit k) | |
37 | (set! mw:renaming-counter 0) | |
38 | (mw:desugar-definitions def-or-exp mw:global-syntax-environment)))) | |
39 | ||
40 | (define (mw:desugar-definitions exp env) | |
41 | (letrec | |
42 | ((define-loop | |
43 | (lambda (exp rest first) | |
44 | (cond ((and (pair? exp) | |
45 | (eq? (mw:syntax-lookup env (car exp)) | |
46 | mw:denote-of-begin) | |
47 | (pair? (cdr exp))) | |
48 | (define-loop (cadr exp) (append (cddr exp) rest) first)) | |
49 | ((and (pair? exp) | |
50 | (eq? (mw:syntax-lookup env (car exp)) | |
51 | mw:denote-of-define)) | |
52 | (let ((exp (desugar-define exp env))) | |
53 | (cond ((and (null? first) (null? rest)) | |
54 | exp) | |
55 | ((null? rest) | |
56 | (cons mw:begin1 (reverse (cons exp first)))) | |
57 | (else (define-loop (car rest) | |
58 | (cdr rest) | |
59 | (cons exp first)))))) | |
60 | ((and (pair? exp) | |
61 | (eq? (mw:syntax-lookup env (car exp)) | |
62 | mw:denote-of-define-syntax) | |
63 | (null? first)) | |
64 | (define-syntax-loop exp rest)) | |
65 | ((and (null? first) (null? rest)) | |
66 | (mw:expand exp env)) | |
67 | ((null? rest) | |
68 | (cons mw:begin1 (reverse (cons (mw:expand exp env) first)))) | |
69 | (else (cons mw:begin1 | |
70 | (append (reverse first) | |
71 | (map (lambda (exp) (mw:expand exp env)) | |
72 | (cons exp rest)))))))) | |
73 | ||
74 | (desugar-define | |
75 | (lambda (exp env) | |
76 | (cond | |
77 | ((null? (cdr exp)) (mw:error "Malformed definition" exp)) | |
78 | ; (define foo) syntax is transformed into (define foo (undefined)). | |
79 | ((null? (cddr exp)) | |
80 | (let ((id (cadr exp))) | |
81 | (redefinition id) | |
82 | (mw:syntax-bind-globally! id (mw:make-identifier-denotation id)) | |
83 | (list mw:define1 id mw:undefined))) | |
84 | ((pair? (cadr exp)) | |
85 | ; mw:lambda0 is an unforgeable lambda, needed here because the | |
86 | ; lambda expression will undergo further expansion. | |
87 | (desugar-define `(,mw:define1 ,(car (cadr exp)) | |
88 | (,mw:lambda0 ,(cdr (cadr exp)) | |
89 | ,@(cddr exp))) | |
90 | env)) | |
91 | ((> (length exp) 3) (mw:error "Malformed definition" exp)) | |
92 | (else (let ((id (cadr exp))) | |
93 | (redefinition id) | |
94 | (mw:syntax-bind-globally! id (mw:make-identifier-denotation id)) | |
95 | `(,mw:define1 ,id ,(mw:expand (caddr exp) env))))))) | |
96 | ||
97 | (define-syntax-loop | |
98 | (lambda (exp rest) | |
99 | (cond ((and (pair? exp) | |
100 | (eq? (mw:syntax-lookup env (car exp)) | |
101 | mw:denote-of-begin) | |
102 | (pair? (cdr exp))) | |
103 | (define-syntax-loop (cadr exp) (append (cddr exp) rest))) | |
104 | ((and (pair? exp) | |
105 | (eq? (mw:syntax-lookup env (car exp)) | |
106 | mw:denote-of-define-syntax)) | |
107 | (if (pair? (cdr exp)) | |
108 | (redefinition (cadr exp))) | |
109 | (if (null? rest) | |
110 | (mw:define-syntax exp env) | |
111 | (begin (mw:define-syntax exp env) | |
112 | (define-syntax-loop (car rest) (cdr rest))))) | |
113 | ((null? rest) | |
114 | (mw:expand exp env)) | |
115 | (else (cons mw:begin1 | |
116 | (map (lambda (exp) (mw:expand exp env)) | |
117 | (cons exp rest))))))) | |
118 | ||
119 | (redefinition | |
120 | (lambda (id) | |
121 | (if (symbol? id) | |
122 | (if (not (mw:identifier? | |
123 | (mw:syntax-lookup mw:global-syntax-environment id))) | |
124 | (mw:warn "Redefining keyword" id)) | |
125 | (mw:error "Malformed variable or keyword" id))))) | |
126 | ||
127 | ; body of letrec | |
128 | ||
129 | (define-loop exp '() '()))) | |
130 | ||
131 | ; Given an expression and a syntactic environment, | |
132 | ; returns an expression in core Scheme. | |
133 | ||
134 | (define (mw:expand exp env) | |
135 | (if (not (pair? exp)) | |
136 | (mw:atom exp env) | |
137 | (let ((keyword (mw:syntax-lookup env (car exp)))) | |
138 | (case (mw:denote-class keyword) | |
139 | ((special) | |
140 | (cond | |
141 | ((eq? keyword mw:denote-of-quote) (mw:quote exp)) | |
142 | ((eq? keyword mw:denote-of-lambda) (mw:lambda exp env)) | |
143 | ((eq? keyword mw:denote-of-if) (mw:if exp env)) | |
144 | ((eq? keyword mw:denote-of-set!) (mw:set exp env)) | |
145 | ((eq? keyword mw:denote-of-begin) (mw:begin exp env)) | |
146 | ((eq? keyword mw:denote-of-let-syntax) (mw:let-syntax exp env)) | |
147 | ((eq? keyword mw:denote-of-letrec-syntax) | |
148 | (mw:letrec-syntax exp env)) | |
149 | ; @@ case has a nontrivial syntax also -- wdc | |
150 | ((eq? keyword mw:denote-of-case) (mw:case exp env)) | |
151 | ; @@ let, let*, letrec, paint within quasiquotation -- kend | |
152 | ((eq? keyword mw:denote-of-let) (mw:let exp env)) | |
153 | ((eq? keyword mw:denote-of-let*) (mw:let* exp env)) | |
154 | ((eq? keyword mw:denote-of-letrec) (mw:letrec exp env)) | |
155 | ((eq? keyword mw:denote-of-quasiquote) (mw:quasiquote exp env)) | |
156 | ((eq? keyword mw:denote-of-do) (mw:do exp env)) | |
157 | ((or (eq? keyword mw:denote-of-define) | |
158 | (eq? keyword mw:denote-of-define-syntax)) | |
159 | ;; slight hack to allow expansion into defines -KenD | |
160 | (if mw:in-define? | |
161 | (mw:error "Definition out of context" exp) | |
162 | (begin | |
163 | (set! mw:in-define? #t) | |
164 | (let ( (result (mw:desugar-definitions exp env)) ) | |
165 | (set! mw:in-define? #f) | |
166 | result)) | |
167 | )) | |
168 | (else (mw:bug "Bug detected in mw:expand" exp env)))) | |
169 | ((macro) (mw:macro exp env)) | |
170 | ((identifier) (mw:application exp env)) | |
171 | (else (mw:bug "Bug detected in mw:expand" exp env)) | |
172 | ) ) | |
173 | ) ) | |
174 | ||
175 | (define mw:in-define? #f) ; should be fluid | |
176 | ||
177 | (define (mw:atom exp env) | |
178 | (cond ((not (symbol? exp)) | |
179 | ; Here exp ought to be a boolean, number, character, or string, | |
180 | ; but I'll allow for non-standard extensions by passing exp | |
181 | ; to the underlying Scheme system without further checking. | |
182 | exp) | |
183 | (else (let ((denotation (mw:syntax-lookup env exp))) | |
184 | (case (mw:denote-class denotation) | |
185 | ((special macro) | |
186 | (mw:error "Syntactic keyword used as a variable" exp env)) | |
187 | ((identifier) (mw:identifier-name denotation)) | |
188 | (else (mw:bug "Bug detected by mw:atom" exp env))))))) | |
189 | ||
190 | (define (mw:quote exp) | |
191 | (if (= (mw:safe-length exp) 2) | |
192 | (list mw:quote1 (mw:strip (cadr exp))) | |
193 | (mw:error "Malformed quoted constant" exp))) | |
194 | ||
195 | (define (mw:lambda exp env) | |
196 | (if (> (mw:safe-length exp) 2) | |
197 | (let* ((formals (cadr exp)) | |
198 | (alist (mw:rename-vars (mw:make-null-terminated formals))) | |
199 | (env (mw:syntax-rename env alist)) | |
200 | (body (cddr exp))) | |
201 | (list mw:lambda1 | |
202 | (mw:rename-formals formals alist) | |
203 | (mw:body body env))) | |
204 | (mw:error "Malformed lambda expression" exp))) | |
205 | ||
206 | (define (mw:body body env) | |
207 | (define (loop body env defs) | |
208 | (if (null? body) | |
209 | (mw:error "Empty body")) | |
210 | (let ((exp (car body))) | |
211 | (if (and (pair? exp) | |
212 | (symbol? (car exp))) | |
213 | (let ((denotation (mw:syntax-lookup env (car exp)))) | |
214 | (case (mw:denote-class denotation) | |
215 | ((special) | |
216 | (cond ((eq? denotation mw:denote-of-begin) | |
217 | (loop (append (cdr exp) (cdr body)) env defs)) | |
218 | ((eq? denotation mw:denote-of-define) | |
219 | (loop (cdr body) env (cons exp defs))) | |
220 | (else (mw:finalize-body body env defs)))) | |
221 | ((macro) | |
222 | (mw:transcribe exp | |
223 | env | |
224 | (lambda (exp env) | |
225 | (loop (cons exp (cdr body)) | |
226 | env | |
227 | defs)))) | |
228 | ((identifier) | |
229 | (mw:finalize-body body env defs)) | |
230 | (else (mw:bug "Bug detected in mw:body" body env)))) | |
231 | (mw:finalize-body body env defs)))) | |
232 | (loop body env '())) | |
233 | ||
234 | (define (mw:finalize-body body env defs) | |
235 | (if (null? defs) | |
236 | (let ((body (map (lambda (exp) (mw:expand exp env)) | |
237 | body))) | |
238 | (if (null? (cdr body)) | |
239 | (car body) | |
240 | (cons mw:begin1 body))) | |
241 | (let* ((alist (mw:rename-vars '(quote lambda set!))) | |
242 | (env (mw:syntax-alias env alist mw:standard-syntax-environment)) | |
243 | (new-quote (cdr (assq 'quote alist))) | |
244 | (new-lambda (cdr (assq 'lambda alist))) | |
245 | (new-set! (cdr (assq 'set! alist)))) | |
246 | (define (desugar-definition def) | |
247 | (if (> (mw:safe-length def) 2) | |
248 | (cond ((pair? (cadr def)) | |
249 | (desugar-definition | |
250 | `(,(car def) | |
251 | ,(car (cadr def)) | |
252 | (,new-lambda | |
253 | ,(cdr (cadr def)) | |
254 | ,@(cddr def))))) | |
255 | ((= (length def) 3) | |
256 | (cdr def)) | |
257 | (else (mw:error "Malformed definition" def env))) | |
258 | (mw:error "Malformed definition" def env))) | |
259 | (mw:letrec | |
260 | `(letrec ,(map desugar-definition (reverse defs)) ,@body) | |
261 | env))) | |
262 | ) | |
263 | ||
264 | (define (mw:if exp env) | |
265 | (let ((n (mw:safe-length exp))) | |
266 | (if (or (= n 3) (= n 4)) | |
267 | (cons mw:if1 (map (lambda (exp) (mw:expand exp env)) (cdr exp))) | |
268 | (mw:error "Malformed if expression" exp env)))) | |
269 | ||
270 | (define (mw:set exp env) | |
271 | (if (= (mw:safe-length exp) 3) | |
272 | `(,mw:set!1 ,(mw:expand (cadr exp) env) ,(mw:expand (caddr exp) env)) | |
273 | (mw:error "Malformed assignment" exp env))) | |
274 | ||
275 | (define (mw:begin exp env) | |
276 | (if (positive? (mw:safe-length exp)) | |
277 | `(,mw:begin1 ,@(map (lambda (exp) (mw:expand exp env)) (cdr exp))) | |
278 | (mw:error "Malformed begin expression" exp env))) | |
279 | ||
280 | (define (mw:application exp env) | |
281 | (if (> (mw:safe-length exp) 0) | |
282 | (map (lambda (exp) (mw:expand exp env)) | |
283 | exp) | |
284 | (mw:error "Malformed application"))) | |
285 | ||
286 | ; I think the environment argument should always be global here. | |
287 | ||
288 | (define (mw:define-syntax exp env) | |
289 | (cond ((and (= (mw:safe-length exp) 3) | |
290 | (symbol? (cadr exp))) | |
291 | (mw:define-syntax1 (cadr exp) | |
292 | (caddr exp) | |
293 | env | |
294 | (mw:define-syntax-scope))) | |
295 | ((and (= (mw:safe-length exp) 4) | |
296 | (symbol? (cadr exp)) | |
297 | (memq (caddr exp) '(letrec letrec* let*))) | |
298 | (mw:define-syntax1 (cadr exp) | |
299 | (cadddr exp) | |
300 | env | |
301 | (caddr exp))) | |
302 | (else (mw:error "Malformed define-syntax" exp env)))) | |
303 | ||
304 | (define (mw:define-syntax1 keyword spec env scope) | |
305 | (case scope | |
306 | ((letrec) (mw:define-syntax-letrec keyword spec env)) | |
307 | ((letrec*) (mw:define-syntax-letrec* keyword spec env)) | |
308 | ((let*) (mw:define-syntax-let* keyword spec env)) | |
309 | (else (mw:bug "Weird scope" scope))) | |
310 | (list mw:quote1 keyword)) | |
311 | ||
312 | (define (mw:define-syntax-letrec keyword spec env) | |
313 | (mw:syntax-bind-globally! | |
314 | keyword | |
315 | (mw:compile-transformer-spec spec env))) | |
316 | ||
317 | (define (mw:define-syntax-letrec* keyword spec env) | |
318 | (let* ((env (mw:syntax-extend (mw:syntax-copy env) | |
319 | (list keyword) | |
320 | '((fake denotation)))) | |
321 | (transformer (mw:compile-transformer-spec spec env))) | |
322 | (mw:syntax-assign! env keyword transformer) | |
323 | (mw:syntax-bind-globally! keyword transformer))) | |
324 | ||
325 | (define (mw:define-syntax-let* keyword spec env) | |
326 | (mw:syntax-bind-globally! | |
327 | keyword | |
328 | (mw:compile-transformer-spec spec (mw:syntax-copy env)))) | |
329 | ||
330 | (define (mw:let-syntax exp env) | |
331 | (if (and (> (mw:safe-length exp) 2) | |
332 | (comlist:every (lambda (binding) | |
333 | (and (pair? binding) | |
334 | (symbol? (car binding)) | |
335 | (pair? (cdr binding)) | |
336 | (null? (cddr binding)))) | |
337 | (cadr exp))) | |
338 | (mw:body (cddr exp) | |
339 | (mw:syntax-extend env | |
340 | (map car (cadr exp)) | |
341 | (map (lambda (spec) | |
342 | (mw:compile-transformer-spec | |
343 | spec | |
344 | env)) | |
345 | (map cadr (cadr exp))))) | |
346 | (mw:error "Malformed let-syntax" exp env))) | |
347 | ||
348 | (define (mw:letrec-syntax exp env) | |
349 | (if (and (> (mw:safe-length exp) 2) | |
350 | (comlist:every (lambda (binding) | |
351 | (and (pair? binding) | |
352 | (symbol? (car binding)) | |
353 | (pair? (cdr binding)) | |
354 | (null? (cddr binding)))) | |
355 | (cadr exp))) | |
356 | (let ((env (mw:syntax-extend env | |
357 | (map car (cadr exp)) | |
358 | (map (lambda (id) | |
359 | '(fake denotation)) | |
360 | (cadr exp))))) | |
361 | (for-each (lambda (id spec) | |
362 | (mw:syntax-assign! | |
363 | env | |
364 | id | |
365 | (mw:compile-transformer-spec spec env))) | |
366 | (map car (cadr exp)) | |
367 | (map cadr (cadr exp))) | |
368 | (mw:body (cddr exp) env)) | |
369 | (mw:error "Malformed let-syntax" exp env))) | |
370 | ||
371 | (define (mw:macro exp env) | |
372 | (mw:transcribe exp | |
373 | env | |
374 | (lambda (exp env) | |
375 | (mw:expand exp env)))) | |
376 | ||
377 | ; To do: | |
378 | ; Clean up alist hacking et cetera. | |
379 | ||
380 | ;;----------------------------------------------------------------- | |
381 | ;; The following was added to allow expansion without flattening | |
382 | ;; LETs to LAMBDAs so that the origianl structure of the program | |
383 | ;; is preserved by macro expansion. I.e. so that usual.scm is not | |
384 | ;; required. -- added KenD | |
385 | ||
386 | (define (mw:process-let-bindings alist binding-list env) ;; helper proc | |
387 | (map (lambda (bind) | |
388 | (list (cdr (assq (car bind) alist)) ; renamed name | |
389 | (mw:body (cdr bind) env))) ; alpha renamed value expression | |
390 | binding-list) | |
391 | ) | |
392 | ||
393 | (define (mw:strip-begin exp) ;; helper proc: mw:body sometimes puts one in | |
394 | (if (and (pair? exp) (eq? (car exp) 'begin)) | |
395 | (cdr exp) | |
396 | exp) | |
397 | ) | |
398 | ||
399 | ; CASE -- added by wdc | |
400 | (define (mw:case exp env) | |
401 | (let ((expand (lambda (exp) | |
402 | (mw:expand exp env)))) | |
403 | (if (< (mw:safe-length exp) 3) | |
404 | (mw:error "Malformed case expression" exp env) | |
405 | `(case ,(expand (cadr exp)) | |
406 | ,@(map (lambda (clause) | |
407 | (if (< (mw:safe-length exp) 2) | |
408 | (mw:error "Malformed case clause" exp env) | |
409 | (cons (mw:strip (car clause)) | |
410 | (map expand (cdr clause))))) | |
411 | (cddr exp)))))) | |
412 | ||
413 | ||
414 | ; LET | |
415 | (define (mw:let exp env) | |
416 | (let* ( (name (if (or (pair? (cadr exp)) (null? (cadr exp))) | |
417 | #f | |
418 | (cadr exp))) ; named let? | |
419 | (binds (if name (caddr exp) (cadr exp))) | |
420 | (body (if name (cdddr exp) (cddr exp))) | |
421 | (vars (if (null? binds) #f (map car binds))) | |
422 | (alist (if vars (mw:rename-vars vars) #f)) | |
423 | (newenv (if alist (mw:syntax-rename env alist) env)) | |
424 | ) | |
425 | (if name ;; extend env with new name | |
426 | (let ( (rename (mw:rename-vars (list name))) ) | |
427 | (set! alist (append rename alist)) | |
428 | (set! newenv (mw:syntax-rename newenv rename)) | |
429 | ) ) | |
430 | `(let | |
431 | ,@(if name (list (cdr (assq name alist))) '()) | |
432 | ,(mw:process-let-bindings alist binds env) | |
433 | ,(mw:body body newenv)) | |
434 | ) ) | |
435 | ||
436 | ||
437 | ; LETREC differs from LET in that the binding values are processed in the | |
438 | ; new rather than the original environment. | |
439 | ||
440 | (define (mw:letrec exp env) | |
441 | (let* ( (binds (cadr exp)) | |
442 | (body (cddr exp)) | |
443 | (vars (if (null? binds) #f (map car binds))) | |
444 | (alist (if vars (mw:rename-vars vars) #f)) | |
445 | (newenv (if alist (mw:syntax-rename env alist) env)) | |
446 | ) | |
447 | `(letrec | |
448 | ,(mw:process-let-bindings alist binds newenv) | |
449 | ,(mw:body body newenv)) | |
450 | ) ) | |
451 | ||
452 | ||
453 | ; LET* adds to ENV for each new binding. | |
454 | ||
455 | (define (mw:let* exp env) | |
456 | (let ( (binds (cadr exp)) | |
457 | (body (cddr exp)) | |
458 | ) | |
459 | (let bind-loop ( (bindings binds) (newbinds '()) (newenv env) ) | |
460 | (if (null? bindings) | |
461 | `(let* ,(reverse newbinds) ,(mw:body body newenv)) | |
462 | (let* ( (bind (car bindings)) | |
463 | (var (car bind)) | |
464 | (valexp (cdr bind)) | |
465 | (rename (mw:rename-vars (list var))) | |
466 | (next-newenv (mw:syntax-rename newenv rename)) | |
467 | ) | |
468 | (bind-loop (cdr bindings) | |
469 | (cons (list (cdr (assq var rename)) | |
470 | (mw:body valexp newenv)) | |
471 | newbinds) | |
472 | next-newenv)) | |
473 | ) ) ) ) | |
474 | ||
475 | ||
476 | ; DO | |
477 | ||
478 | (define (mw:process-do-bindings var-init-steps alist oldenv newenv) ;; helper proc | |
479 | (map (lambda (vis) | |
480 | (let ( (v (car vis)) | |
481 | (i (cadr vis)) | |
482 | (s (if (null? (cddr vis)) (car vis) (caddr vis)))) | |
483 | `( ,(cdr (assq v alist)) ; renamed name | |
484 | ,(mw:body (list i) oldenv) ; init in outer/old env | |
485 | ,(mw:body (list s) newenv) ))) ; step in letrec/inner/new env | |
486 | var-init-steps) | |
487 | ) | |
488 | ||
489 | (define (mw:do exp env) | |
490 | (let* ( (vis (cadr exp)) ; (Var Init Step ...) | |
491 | (ts (caddr exp)) ; (Test Sequence ...) | |
492 | (com (cdddr exp)) ; (COMmand ...) | |
493 | (vars (if (null? vis) #f (map car vis))) | |
494 | (rename (if vars (mw:rename-vars vars) #f)) | |
495 | (newenv (if vars (mw:syntax-rename env rename) env)) | |
496 | ) | |
497 | `(do ,(if vars (mw:process-do-bindings vis rename env newenv) '()) | |
498 | ,(if (null? ts) '() (mw:strip-begin (mw:body (list ts) newenv))) | |
499 | ,@(if (null? com) '() (list (mw:body com newenv)))) | |
500 | ) ) | |
501 | ||
502 | ; | |
503 | ; Quasiquotation (backquote) | |
504 | ; | |
505 | ; At level 0, unquoted forms are left painted (not mw:strip'ed). | |
506 | ; At higher levels, forms which are unquoted to level 0 are painted. | |
507 | ; This includes forms within quotes. E.g.: | |
508 | ; (lambda (a) | |
509 | ; (quasiquote | |
510 | ; (a (unquote a) b (quasiquote (a (unquote (unquote a)) b))))) | |
511 | ;or equivalently: | |
512 | ; (lambda (a) `(a ,a b `(a ,,a b))) | |
513 | ;=> | |
514 | ; (lambda (a|1) `(a ,a|1 b `(a ,,a|1 b))) | |
515 | ||
516 | (define (mw:quasiquote exp env) | |
517 | ||
518 | (define (mw:atom exp env) | |
519 | (if (not (symbol? exp)) | |
520 | exp | |
521 | (let ((denotation (mw:syntax-lookup env exp))) | |
522 | (case (mw:denote-class denotation) | |
523 | ((special macro identifier) (mw:identifier-name denotation)) | |
524 | (else (mw:bug "Bug detected by mw:atom" exp env)))) | |
525 | ) ) | |
526 | ||
527 | (define (quasi subexp level) | |
528 | (cond | |
529 | ((null? subexp) subexp) | |
530 | ((not (or (pair? subexp) (vector? subexp))) | |
531 | (if (zero? level) (mw:atom subexp env) subexp) ; the work is here | |
532 | ) | |
533 | ((vector? subexp) | |
534 | (let* ((l (vector-length subexp)) | |
535 | (v (make-vector l))) | |
536 | (do ((i 0 (+ i 1))) | |
537 | ((= i l) v) | |
538 | (vector-set! v i (quasi (vector-ref subexp i) level)) | |
539 | ) | |
540 | ) | |
541 | ) | |
542 | (else | |
543 | (let ( (keyword (mw:syntax-lookup env (car subexp))) ) | |
544 | (cond | |
545 | ((eq? keyword mw:denote-of-unquote) | |
546 | (cons 'unquote (quasi (cdr subexp) (- level 1))) | |
547 | ) | |
548 | ((eq? keyword mw:denote-of-unquote-splicing) | |
549 | (cons 'unquote-splicing (quasi (cdr subexp) (- level 1))) | |
550 | ) | |
551 | ((eq? keyword mw:denote-of-quasiquote) | |
552 | (cons 'quasiquote (quasi (cdr subexp) (+ level 1))) | |
553 | ) | |
554 | (else | |
555 | (cons (quasi (car subexp) level) (quasi (cdr subexp) level)) | |
556 | ) | |
557 | ) | |
558 | ) ) ; end else, let | |
559 | ) ; end cond | |
560 | ) | |
561 | ||
562 | (quasi exp 0) ; need to unquote to level 0 to paint | |
563 | ) | |
564 | ||
565 | ;; --- E O F --- |