1 665c255d 2023-08-04 jrmu (define (ambeval exp env succeed fail)
2 665c255d 2023-08-04 jrmu ((analyze exp) env succeed fail))
3 665c255d 2023-08-04 jrmu (define (analyze exp)
4 665c255d 2023-08-04 jrmu (cond ((self-evaluating? exp)
5 665c255d 2023-08-04 jrmu (analyze-self-evaluating exp))
6 665c255d 2023-08-04 jrmu ((quoted? exp) (analyze-quoted exp))
7 665c255d 2023-08-04 jrmu ((variable? exp) (analyze-variable exp))
8 665c255d 2023-08-04 jrmu ((assignment? exp) (analyze-assignment exp))
9 665c255d 2023-08-04 jrmu ((definition? exp) (analyze-definition exp))
10 665c255d 2023-08-04 jrmu ((if? exp) (analyze-if exp))
11 665c255d 2023-08-04 jrmu ((and? exp) (analyze (and->if exp)))
12 665c255d 2023-08-04 jrmu ((or? exp) (analyze (or->if exp)))
13 665c255d 2023-08-04 jrmu ((not? exp) (analyze (not->if exp)))
14 665c255d 2023-08-04 jrmu ((xor? exp) (analyze (xor->or-and-not exp)))
15 665c255d 2023-08-04 jrmu ((lambda? exp) (analyze-lambda exp))
16 665c255d 2023-08-04 jrmu ((let? exp) (analyze (let->combination exp)))
17 665c255d 2023-08-04 jrmu ((let*? exp) (analyze (let*->nested-lets exp)))
18 665c255d 2023-08-04 jrmu ((named-let? exp) (analyze (named-let->combination exp)))
19 665c255d 2023-08-04 jrmu ((letrec? exp) (analyze (letrec->let exp)))
20 665c255d 2023-08-04 jrmu ((do? exp) (analyze (do->combination exp)))
21 665c255d 2023-08-04 jrmu ((begin? exp) (analyze-sequence (begin-actions exp)))
22 665c255d 2023-08-04 jrmu ((cond? exp) (analyze (cond->if exp)))
23 665c255d 2023-08-04 jrmu ((amb? exp) (analyze-amb exp))
24 665c255d 2023-08-04 jrmu ((application? exp) (analyze-application exp))
26 665c255d 2023-08-04 jrmu (error "Unknown expression type -- ANALYZE" exp))))
29 665c255d 2023-08-04 jrmu ;; analyzing procedures
30 665c255d 2023-08-04 jrmu (define (analyze-self-evaluating exp)
31 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
32 665c255d 2023-08-04 jrmu (succeed exp fail)))
33 665c255d 2023-08-04 jrmu (define (analyze-quoted exp)
34 665c255d 2023-08-04 jrmu (let ((qval (text-of-quotation exp)))
35 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
36 665c255d 2023-08-04 jrmu (succeed qval fail))))
37 665c255d 2023-08-04 jrmu (define (analyze-variable exp)
38 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
39 665c255d 2023-08-04 jrmu (succeed (lookup-variable-value exp env)
41 665c255d 2023-08-04 jrmu (define (analyze-lambda exp)
42 665c255d 2023-08-04 jrmu (let ((vars (lambda-parameters exp))
43 665c255d 2023-08-04 jrmu ;; (bproc (analyze-sequence (scan-out-defines (lambda-body exp)))))
44 665c255d 2023-08-04 jrmu (bproc (analyze-sequence (lambda-body exp))))
45 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
46 665c255d 2023-08-04 jrmu (succeed (make-procedure vars bproc env)
48 665c255d 2023-08-04 jrmu (define (analyze-if exp)
49 665c255d 2023-08-04 jrmu (let ((pproc (analyze (if-predicate exp)))
50 665c255d 2023-08-04 jrmu (cproc (analyze (if-consequent exp)))
51 665c255d 2023-08-04 jrmu (aproc (analyze (if-alternative exp))))
52 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
54 665c255d 2023-08-04 jrmu ;; success continuation for evaluating the predicate
55 665c255d 2023-08-04 jrmu ;; to obtain pred-value
56 665c255d 2023-08-04 jrmu (lambda (pred-value fail2)
57 665c255d 2023-08-04 jrmu (if (true? pred-value)
58 665c255d 2023-08-04 jrmu (cproc env succeed fail2)
59 665c255d 2023-08-04 jrmu (aproc env succeed fail2)))
60 665c255d 2023-08-04 jrmu ;; failure continuation for evaluating the predicate
62 665c255d 2023-08-04 jrmu (define (analyze-sequence exps)
63 665c255d 2023-08-04 jrmu (define (sequentially a b)
64 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
66 665c255d 2023-08-04 jrmu ;; success continuation for calling a
67 665c255d 2023-08-04 jrmu (lambda (a-value fail2)
68 665c255d 2023-08-04 jrmu (b env succeed fail2))
69 665c255d 2023-08-04 jrmu ;; failure continuation for calling a
71 665c255d 2023-08-04 jrmu (define (loop first-proc rest-procs)
72 665c255d 2023-08-04 jrmu (if (null? rest-procs)
74 665c255d 2023-08-04 jrmu (loop (sequentially first-proc (car rest-procs))
75 665c255d 2023-08-04 jrmu (cdr rest-procs))))
76 665c255d 2023-08-04 jrmu (let ((procs (map analyze exps)))
77 665c255d 2023-08-04 jrmu (if (null? procs)
78 665c255d 2023-08-04 jrmu (error "Empty sequence -- ANALYZE"))
79 665c255d 2023-08-04 jrmu (loop (car procs) (cdr procs))))
80 665c255d 2023-08-04 jrmu (define (analyze-definition exp)
81 665c255d 2023-08-04 jrmu (let ((var (definition-variable exp))
82 665c255d 2023-08-04 jrmu (vproc (analyze (definition-value exp))))
83 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
85 665c255d 2023-08-04 jrmu (lambda (val fail2)
86 665c255d 2023-08-04 jrmu (define-variable! var val env)
87 665c255d 2023-08-04 jrmu (succeed 'ok fail2))
89 665c255d 2023-08-04 jrmu (define (analyze-assignment exp)
90 665c255d 2023-08-04 jrmu (let ((var (assignment-variable exp))
91 665c255d 2023-08-04 jrmu (vproc (analyze (assignment-value exp))))
92 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
94 665c255d 2023-08-04 jrmu (lambda (val fail2) ; *1*
95 665c255d 2023-08-04 jrmu (let ((old-value
96 665c255d 2023-08-04 jrmu (lookup-variable-value var env)))
97 665c255d 2023-08-04 jrmu (set-variable-value! var val env)
98 665c255d 2023-08-04 jrmu (succeed 'ok
99 665c255d 2023-08-04 jrmu (lambda () ; *2*
100 665c255d 2023-08-04 jrmu (set-variable-value! var
103 665c255d 2023-08-04 jrmu (fail2)))))
106 665c255d 2023-08-04 jrmu (define (analyze-application exp)
107 665c255d 2023-08-04 jrmu (let ((fproc (analyze (operator exp)))
108 665c255d 2023-08-04 jrmu (aprocs (map analyze (operands exp))))
109 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
111 665c255d 2023-08-04 jrmu (lambda (proc fail2)
112 665c255d 2023-08-04 jrmu (get-args aprocs
114 665c255d 2023-08-04 jrmu (lambda (args fail3)
115 665c255d 2023-08-04 jrmu (execute-application
116 665c255d 2023-08-04 jrmu proc args succeed fail3))
119 665c255d 2023-08-04 jrmu (define (get-args aprocs env succeed fail)
120 665c255d 2023-08-04 jrmu (if (null? aprocs)
121 665c255d 2023-08-04 jrmu (succeed '() fail)
122 665c255d 2023-08-04 jrmu ((car aprocs) env
123 665c255d 2023-08-04 jrmu ;; success continuation for this aproc
124 665c255d 2023-08-04 jrmu (lambda (arg fail2)
125 665c255d 2023-08-04 jrmu (get-args (cdr aprocs)
127 665c255d 2023-08-04 jrmu ;; success continuation for recursive
128 665c255d 2023-08-04 jrmu ;; call to get-args
129 665c255d 2023-08-04 jrmu (lambda (args fail3)
130 665c255d 2023-08-04 jrmu (succeed (cons arg args)
135 665c255d 2023-08-04 jrmu (define (analyze-amb exp)
136 665c255d 2023-08-04 jrmu (let ((cprocs (map analyze (amb-choices exp))))
137 665c255d 2023-08-04 jrmu (lambda (env succeed fail)
138 665c255d 2023-08-04 jrmu (define (try-next choices)
139 665c255d 2023-08-04 jrmu (if (null? choices)
141 665c255d 2023-08-04 jrmu ((car choices) env
144 665c255d 2023-08-04 jrmu (try-next (cdr choices))))))
145 665c255d 2023-08-04 jrmu (try-next cprocs))))
152 665c255d 2023-08-04 jrmu (define (tagged-list? exp tag)
153 665c255d 2023-08-04 jrmu (if (pair? exp)
154 665c255d 2023-08-04 jrmu (eq? (car exp) tag)
158 665c255d 2023-08-04 jrmu (define (amb? exp) (tagged-list? exp 'amb))
159 665c255d 2023-08-04 jrmu (define (amb-choices exp) (cdr exp))
161 665c255d 2023-08-04 jrmu ;; self-evaluating/variable/quoted
162 665c255d 2023-08-04 jrmu (define (self-evaluating? exp)
163 665c255d 2023-08-04 jrmu (cond ((number? exp) true)
164 665c255d 2023-08-04 jrmu ((string? exp) true)
165 665c255d 2023-08-04 jrmu (else false)))
166 665c255d 2023-08-04 jrmu (define (variable? exp) (symbol? exp))
167 665c255d 2023-08-04 jrmu (define (quoted? exp)
168 665c255d 2023-08-04 jrmu (tagged-list? exp 'quote))
169 665c255d 2023-08-04 jrmu (define (text-of-quotation exp) (cadr exp))
171 665c255d 2023-08-04 jrmu ;; assignment/definition
172 665c255d 2023-08-04 jrmu (define (assignment? exp)
173 665c255d 2023-08-04 jrmu (tagged-list? exp 'set!))
174 665c255d 2023-08-04 jrmu (define (assignment-variable exp) (cadr exp))
175 665c255d 2023-08-04 jrmu (define (assignment-value exp) (caddr exp))
176 665c255d 2023-08-04 jrmu (define (make-assignment var val)
177 665c255d 2023-08-04 jrmu (list 'set! var val))
178 665c255d 2023-08-04 jrmu (define (definition? exp)
179 665c255d 2023-08-04 jrmu (tagged-list? exp 'define))
180 665c255d 2023-08-04 jrmu (define (definition-variable exp)
181 665c255d 2023-08-04 jrmu (if (symbol? (cadr exp))
183 665c255d 2023-08-04 jrmu (caadr exp)))
184 665c255d 2023-08-04 jrmu (define (definition-value exp)
185 665c255d 2023-08-04 jrmu (if (symbol? (cadr exp))
186 665c255d 2023-08-04 jrmu (caddr exp)
187 665c255d 2023-08-04 jrmu (make-lambda (cdadr exp) ; formal parameters
188 665c255d 2023-08-04 jrmu (cddr exp)))) ; body
189 665c255d 2023-08-04 jrmu (define (make-definition var val)
190 665c255d 2023-08-04 jrmu `(define ,var ,val))
192 665c255d 2023-08-04 jrmu ;; if/and/or/not/xor
193 665c255d 2023-08-04 jrmu (define (if? exp) (tagged-list? exp 'if))
194 665c255d 2023-08-04 jrmu (define (if-predicate exp) (cadr exp))
195 665c255d 2023-08-04 jrmu (define (if-consequent exp) (caddr exp))
196 665c255d 2023-08-04 jrmu (define (if-alternative exp)
197 665c255d 2023-08-04 jrmu (if (not (null? (cdddr exp)))
198 665c255d 2023-08-04 jrmu (cadddr exp)
200 665c255d 2023-08-04 jrmu (define (make-if predicate consequent alternative)
201 665c255d 2023-08-04 jrmu (list 'if predicate consequent alternative))
203 665c255d 2023-08-04 jrmu (define (and? exp)
204 665c255d 2023-08-04 jrmu (tagged-list? exp 'and))
205 665c255d 2023-08-04 jrmu (define (and-clauses exp)
207 665c255d 2023-08-04 jrmu (define (or? exp)
208 665c255d 2023-08-04 jrmu (tagged-list? exp 'or))
209 665c255d 2023-08-04 jrmu (define (or-clauses exp)
211 665c255d 2023-08-04 jrmu (define (and->if exp)
212 665c255d 2023-08-04 jrmu (define (expand-clauses clauses)
213 665c255d 2023-08-04 jrmu (cond ((null? clauses) 'true)
214 665c255d 2023-08-04 jrmu ((null? (cdr clauses)) (car clauses))
215 665c255d 2023-08-04 jrmu (else (make-if (car clauses)
216 665c255d 2023-08-04 jrmu (expand-clauses (cdr clauses))
218 665c255d 2023-08-04 jrmu (expand-clauses (and-clauses exp)))
219 665c255d 2023-08-04 jrmu (define (or->if exp)
220 665c255d 2023-08-04 jrmu (define (expand-clauses clauses)
221 665c255d 2023-08-04 jrmu (if (null? clauses)
223 665c255d 2023-08-04 jrmu (make-if (car clauses)
224 665c255d 2023-08-04 jrmu (car clauses)
225 665c255d 2023-08-04 jrmu (expand-clauses (cdr clauses)))))
226 665c255d 2023-08-04 jrmu (expand-clauses (or-clauses exp)))
227 665c255d 2023-08-04 jrmu (define (not? exp)
228 665c255d 2023-08-04 jrmu (tagged-list? exp 'not))
229 665c255d 2023-08-04 jrmu (define (not->if exp)
230 665c255d 2023-08-04 jrmu `(if ,(cadr exp) false true))
231 665c255d 2023-08-04 jrmu (define (xor? exp)
232 665c255d 2023-08-04 jrmu (tagged-list? exp 'xor))
233 665c255d 2023-08-04 jrmu (define (xor->or-and-not exp)
234 665c255d 2023-08-04 jrmu (let ((pred-1 (cadr exp))
235 665c255d 2023-08-04 jrmu (pred-2 (caddr exp)))
236 665c255d 2023-08-04 jrmu `(or (and ,pred-1 (not ,pred-2))
237 665c255d 2023-08-04 jrmu (and (not ,pred-1) ,pred-2))))
239 665c255d 2023-08-04 jrmu ;; lambda/let/let*/letrec
240 665c255d 2023-08-04 jrmu (define (lambda? exp) (tagged-list? exp 'lambda))
241 665c255d 2023-08-04 jrmu (define (lambda-parameters exp) (cadr exp))
242 665c255d 2023-08-04 jrmu (define (lambda-body exp) (cddr exp))
243 665c255d 2023-08-04 jrmu (define (make-lambda parameters body)
244 665c255d 2023-08-04 jrmu (cons 'lambda (cons parameters body)))
246 665c255d 2023-08-04 jrmu (define (make-let vars vals body)
248 665c255d 2023-08-04 jrmu (cons (map list vars vals)
250 665c255d 2023-08-04 jrmu (define (let? exp)
251 665c255d 2023-08-04 jrmu (and (tagged-list? exp 'let)
252 665c255d 2023-08-04 jrmu (not (symbol? (cadr exp)))))
253 665c255d 2023-08-04 jrmu (define (let-vars exp)
254 665c255d 2023-08-04 jrmu (map car (cadr exp)))
255 665c255d 2023-08-04 jrmu (define (let-vals exp)
256 665c255d 2023-08-04 jrmu (map cadr (cadr exp)))
257 665c255d 2023-08-04 jrmu (define (let-body exp)
258 665c255d 2023-08-04 jrmu (cddr exp))
259 665c255d 2023-08-04 jrmu (define (let->combination exp)
260 665c255d 2023-08-04 jrmu (make-application (make-lambda (let-vars exp) (let-body exp))
261 665c255d 2023-08-04 jrmu (let-vals exp)))
262 665c255d 2023-08-04 jrmu (define (named-let? exp)
263 665c255d 2023-08-04 jrmu (and (tagged-list? exp 'let)
264 665c255d 2023-08-04 jrmu (symbol? (cadr exp))))
265 665c255d 2023-08-04 jrmu (define (named-let-name exp)
266 665c255d 2023-08-04 jrmu (cadr exp))
267 665c255d 2023-08-04 jrmu (define (named-let-vars exp)
268 665c255d 2023-08-04 jrmu (map car (caddr exp)))
269 665c255d 2023-08-04 jrmu (define (named-let-vals exp)
270 665c255d 2023-08-04 jrmu (map cadr (caddr exp)))
271 665c255d 2023-08-04 jrmu (define (named-let-body exp)
272 665c255d 2023-08-04 jrmu (cdddr exp))
273 665c255d 2023-08-04 jrmu (define (named-let->combination exp)
274 665c255d 2023-08-04 jrmu (sequence->exp
275 665c255d 2023-08-04 jrmu (list (make-definition (named-let-name exp)
276 665c255d 2023-08-04 jrmu (make-lambda (named-let-vars exp)
277 665c255d 2023-08-04 jrmu (named-let-body exp)))
278 665c255d 2023-08-04 jrmu (make-application (named-let-name exp)
279 665c255d 2023-08-04 jrmu (named-let-vals exp)))))
280 665c255d 2023-08-04 jrmu (define (make-named-let name vars vals body)
283 665c255d 2023-08-04 jrmu (cons (map list vars vals)
286 665c255d 2023-08-04 jrmu (define (letrec? exp)
287 665c255d 2023-08-04 jrmu (tagged-list? exp 'letrec))
289 665c255d 2023-08-04 jrmu (define (letrec-vars exp)
290 665c255d 2023-08-04 jrmu (map car (cadr exp)))
291 665c255d 2023-08-04 jrmu (define (letrec-vals exp)
292 665c255d 2023-08-04 jrmu (map cadr (cadr exp)))
293 665c255d 2023-08-04 jrmu (define (letrec-body exp)
294 665c255d 2023-08-04 jrmu (cddr exp))
295 665c255d 2023-08-04 jrmu (define (letrec->let exp)
296 665c255d 2023-08-04 jrmu (let* ((vars (letrec-vars exp))
297 665c255d 2023-08-04 jrmu (unassigneds (map (lambda (var) ''*unassigned*)
299 665c255d 2023-08-04 jrmu (vals (letrec-vals exp))
300 665c255d 2023-08-04 jrmu (assignments (map (lambda (var val)
301 665c255d 2023-08-04 jrmu (make-assignment var val))
304 665c255d 2023-08-04 jrmu (body (letrec-body exp)))
305 665c255d 2023-08-04 jrmu (make-let vars
306 665c255d 2023-08-04 jrmu unassigneds
307 665c255d 2023-08-04 jrmu (append assignments body))))
309 665c255d 2023-08-04 jrmu (define (make-application op args)
310 665c255d 2023-08-04 jrmu (cons op args))
312 665c255d 2023-08-04 jrmu (define (let*? exp)
313 665c255d 2023-08-04 jrmu (tagged-list? exp 'let*))
314 665c255d 2023-08-04 jrmu (define let*-vars let-vars)
315 665c255d 2023-08-04 jrmu (define let*-vals let-vals)
316 665c255d 2023-08-04 jrmu (define let*-body let-body)
317 665c255d 2023-08-04 jrmu (define (let*->nested-lets exp)
318 665c255d 2023-08-04 jrmu (define (expand-lets vars vals)
319 665c255d 2023-08-04 jrmu (if (null? (cdr vars))
320 665c255d 2023-08-04 jrmu (make-let (list (car vars))
321 665c255d 2023-08-04 jrmu (list (car vals))
322 665c255d 2023-08-04 jrmu (let*-body exp))
323 665c255d 2023-08-04 jrmu (make-let (list (car vars))
324 665c255d 2023-08-04 jrmu (list (car vals))
325 665c255d 2023-08-04 jrmu (list (expand-lets (cdr vars) (cdr vals))))))
326 665c255d 2023-08-04 jrmu (let ((vars (let*-vars exp))
327 665c255d 2023-08-04 jrmu (vals (let*-vals exp)))
328 665c255d 2023-08-04 jrmu (if (null? vars)
329 665c255d 2023-08-04 jrmu (sequence->exp (let*-body exp))
330 665c255d 2023-08-04 jrmu (expand-lets vars vals))))
333 665c255d 2023-08-04 jrmu (define (do? exp)
334 665c255d 2023-08-04 jrmu (tagged-list? exp 'do))
335 665c255d 2023-08-04 jrmu (define (do-vars exp)
336 665c255d 2023-08-04 jrmu (map car (cadr exp)))
337 665c255d 2023-08-04 jrmu (define (do-inits exp)
338 665c255d 2023-08-04 jrmu (map cadr (cadr exp)))
339 665c255d 2023-08-04 jrmu (define (do-steps exp)
340 665c255d 2023-08-04 jrmu (map (lambda (var-init-step)
341 665c255d 2023-08-04 jrmu (if (null? (cddr var-init-step))
342 665c255d 2023-08-04 jrmu (car var-init-step)
343 665c255d 2023-08-04 jrmu (caddr var-init-step)))
344 665c255d 2023-08-04 jrmu (cadr exp)))
345 665c255d 2023-08-04 jrmu (define (do-test exp)
346 665c255d 2023-08-04 jrmu (caaddr exp))
347 665c255d 2023-08-04 jrmu (define (do-expressions exp)
348 665c255d 2023-08-04 jrmu (if (null? (cdaddr exp))
349 665c255d 2023-08-04 jrmu (caddr exp)
350 665c255d 2023-08-04 jrmu (cdaddr exp)))
351 665c255d 2023-08-04 jrmu (define (do-commands exp)
352 665c255d 2023-08-04 jrmu (cdddr exp))
353 665c255d 2023-08-04 jrmu (define (do->combination exp)
354 665c255d 2023-08-04 jrmu (make-named-let
356 665c255d 2023-08-04 jrmu (do-vars exp)
357 665c255d 2023-08-04 jrmu (do-inits exp)
360 665c255d 2023-08-04 jrmu (do-test exp)
361 665c255d 2023-08-04 jrmu (sequence->exp (do-expressions exp))
362 665c255d 2023-08-04 jrmu (sequence->exp
363 665c255d 2023-08-04 jrmu (append (do-commands exp)
364 665c255d 2023-08-04 jrmu (list (make-application
366 665c255d 2023-08-04 jrmu (do-steps exp)))))))))
369 665c255d 2023-08-04 jrmu ;; begin/sequence
370 665c255d 2023-08-04 jrmu (define (begin? exp) (tagged-list? exp 'begin))
371 665c255d 2023-08-04 jrmu (define (begin-actions exp) (cdr exp))
372 665c255d 2023-08-04 jrmu (define (last-exp? seq) (null? (cdr seq)))
373 665c255d 2023-08-04 jrmu (define (first-exp seq) (car seq))
374 665c255d 2023-08-04 jrmu (define (rest-exps seq) (cdr seq))
375 665c255d 2023-08-04 jrmu (define (sequence->exp seq)
376 665c255d 2023-08-04 jrmu (cond ((null? seq) seq)
377 665c255d 2023-08-04 jrmu ((last-exp? seq) (first-exp seq))
378 665c255d 2023-08-04 jrmu (else (make-begin seq))))
379 665c255d 2023-08-04 jrmu (define (make-begin seq) (cons 'begin seq))
381 665c255d 2023-08-04 jrmu ;; application
382 665c255d 2023-08-04 jrmu (define (application? exp) (pair? exp))
383 665c255d 2023-08-04 jrmu (define (operator exp) (car exp))
384 665c255d 2023-08-04 jrmu (define (operands exp) (cdr exp))
385 665c255d 2023-08-04 jrmu (define (no-operands? ops) (null? ops))
386 665c255d 2023-08-04 jrmu (define (first-operand ops) (car ops))
387 665c255d 2023-08-04 jrmu (define (rest-operands ops) (cdr ops))
390 665c255d 2023-08-04 jrmu (define (cond? exp) (tagged-list? exp 'cond))
391 665c255d 2023-08-04 jrmu (define (cond-clauses exp) (cdr exp))
392 665c255d 2023-08-04 jrmu (define (cond-else-clause? clause)
393 665c255d 2023-08-04 jrmu (eq? (cond-predicate clause) 'else))
394 665c255d 2023-08-04 jrmu (define (cond-predicate clause) (car clause))
395 665c255d 2023-08-04 jrmu (define (cond-actions clause) (cdr clause))
396 665c255d 2023-08-04 jrmu (define (cond-extended-clause? clause)
397 665c255d 2023-08-04 jrmu (and (not (null? (cdr clause))) (eq? (cadr clause) '=>)))
398 665c255d 2023-08-04 jrmu (define (cond-extended-proc clause)
399 665c255d 2023-08-04 jrmu (caddr clause))
400 665c255d 2023-08-04 jrmu (define (cond->if exp)
401 665c255d 2023-08-04 jrmu (expand-clauses (cond-clauses exp)))
402 665c255d 2023-08-04 jrmu (define (expand-clauses clauses)
403 665c255d 2023-08-04 jrmu (if (null? clauses)
404 665c255d 2023-08-04 jrmu 'false ; no else clause
405 665c255d 2023-08-04 jrmu (let ((first (car clauses))
406 665c255d 2023-08-04 jrmu (rest (cdr clauses)))
407 665c255d 2023-08-04 jrmu (if (cond-else-clause? first)
408 665c255d 2023-08-04 jrmu (if (null? rest)
409 665c255d 2023-08-04 jrmu (sequence->exp (cond-actions first))
410 665c255d 2023-08-04 jrmu (error "ELSE clause isn't last -- COND->IF"
412 665c255d 2023-08-04 jrmu (if (cond-extended-clause? first)
413 665c255d 2023-08-04 jrmu (make-if (cond-predicate first)
414 665c255d 2023-08-04 jrmu (make-application
415 665c255d 2023-08-04 jrmu (cond-extended-proc first)
416 665c255d 2023-08-04 jrmu (list (cond-predicate first)))
417 665c255d 2023-08-04 jrmu (expand-clauses rest))
418 665c255d 2023-08-04 jrmu (make-if (cond-predicate first)
419 665c255d 2023-08-04 jrmu (sequence->exp (cond-actions first))
420 665c255d 2023-08-04 jrmu (expand-clauses rest)))))))
421 665c255d 2023-08-04 jrmu (define (true? x)
422 665c255d 2023-08-04 jrmu (not (eq? x false)))
423 665c255d 2023-08-04 jrmu (define (false? x)
424 665c255d 2023-08-04 jrmu (eq? x false))
426 665c255d 2023-08-04 jrmu ;; procedure
427 665c255d 2023-08-04 jrmu (define (make-procedure parameters body env)
428 665c255d 2023-08-04 jrmu (list 'procedure parameters body env))
429 665c255d 2023-08-04 jrmu (define (scan-out-defines body)
430 665c255d 2023-08-04 jrmu (let* ((definitions (filter definition? body))
431 665c255d 2023-08-04 jrmu (vars (map definition-variable definitions))
432 665c255d 2023-08-04 jrmu (unassigneds (map (lambda (var) ''*unassigned*)
434 665c255d 2023-08-04 jrmu (vals (map definition-value definitions))
435 665c255d 2023-08-04 jrmu (assignments
436 665c255d 2023-08-04 jrmu (map (lambda (var val)
437 665c255d 2023-08-04 jrmu (make-assignment var val))
438 665c255d 2023-08-04 jrmu vars vals))
439 665c255d 2023-08-04 jrmu (exps (remove definition? body)))
440 665c255d 2023-08-04 jrmu (if (null? definitions)
443 665c255d 2023-08-04 jrmu (make-let vars
444 665c255d 2023-08-04 jrmu unassigneds
445 665c255d 2023-08-04 jrmu (append assignments exps))))))
446 665c255d 2023-08-04 jrmu (define (compound-procedure? p)
447 665c255d 2023-08-04 jrmu (tagged-list? p 'procedure))
448 665c255d 2023-08-04 jrmu (define (procedure-parameters p) (cadr p))
449 665c255d 2023-08-04 jrmu (define (procedure-body p) (caddr p))
450 665c255d 2023-08-04 jrmu (define (procedure-environment p) (cadddr p))
452 665c255d 2023-08-04 jrmu ;; environment
453 665c255d 2023-08-04 jrmu (define (enclosing-environment env) (cdr env))
454 665c255d 2023-08-04 jrmu (define (first-frame env) (car env))
455 665c255d 2023-08-04 jrmu (define the-empty-environment '())
456 665c255d 2023-08-04 jrmu (define (make-frame variables values)
457 665c255d 2023-08-04 jrmu (cons variables values))
458 665c255d 2023-08-04 jrmu (define (frame-variables frame) (car frame))
459 665c255d 2023-08-04 jrmu (define (frame-values frame) (cdr frame))
460 665c255d 2023-08-04 jrmu (define (add-binding-to-frame! var val frame)
461 665c255d 2023-08-04 jrmu (set-car! frame (cons var (car frame)))
462 665c255d 2023-08-04 jrmu (set-cdr! frame (cons val (cdr frame))))
463 665c255d 2023-08-04 jrmu (define (extend-environment vars vals base-env)
464 665c255d 2023-08-04 jrmu (if (= (length vars) (length vals))
465 665c255d 2023-08-04 jrmu (cons (make-frame vars vals) base-env)
466 665c255d 2023-08-04 jrmu (if (< (length vars) (length vals))
467 665c255d 2023-08-04 jrmu (error "Too many arguments supplied" vars vals)
468 665c255d 2023-08-04 jrmu (error "Too few arguments supplied" vars vals))))
469 665c255d 2023-08-04 jrmu (define (lookup-variable-value var env)
470 665c255d 2023-08-04 jrmu (define (env-loop env)
471 665c255d 2023-08-04 jrmu (define (scan vars vals)
472 665c255d 2023-08-04 jrmu (cond ((null? vars)
473 665c255d 2023-08-04 jrmu (env-loop (enclosing-environment env)))
474 665c255d 2023-08-04 jrmu ((eq? var (car vars))
475 665c255d 2023-08-04 jrmu (let ((val (car vals)))
476 665c255d 2023-08-04 jrmu (if (eq? val '*unassigned*)
477 665c255d 2023-08-04 jrmu (error "Var not yet defined -- LOOKUP-VARIABLE-VALUE" var)
479 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
480 665c255d 2023-08-04 jrmu (if (eq? env the-empty-environment)
481 665c255d 2023-08-04 jrmu (error "Unbound variable" var)
482 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
483 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
484 665c255d 2023-08-04 jrmu (frame-values frame)))))
485 665c255d 2023-08-04 jrmu (env-loop env))
486 665c255d 2023-08-04 jrmu (define (set-variable-value! var val env)
487 665c255d 2023-08-04 jrmu (define (env-loop env)
488 665c255d 2023-08-04 jrmu (define (scan vars vals)
489 665c255d 2023-08-04 jrmu (cond ((null? vars)
490 665c255d 2023-08-04 jrmu (env-loop (enclosing-environment env)))
491 665c255d 2023-08-04 jrmu ((eq? var (car vars))
492 665c255d 2023-08-04 jrmu (set-car! vals val))
493 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
494 665c255d 2023-08-04 jrmu (if (eq? env the-empty-environment)
495 665c255d 2023-08-04 jrmu (error "Unbound variable -- SET!" var)
496 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
497 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
498 665c255d 2023-08-04 jrmu (frame-values frame)))))
499 665c255d 2023-08-04 jrmu (env-loop env))
500 665c255d 2023-08-04 jrmu (define (define-variable! var val env)
501 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
502 665c255d 2023-08-04 jrmu (define (scan vars vals)
503 665c255d 2023-08-04 jrmu (cond ((null? vars)
504 665c255d 2023-08-04 jrmu (add-binding-to-frame! var val frame))
505 665c255d 2023-08-04 jrmu ((eq? var (car vars))
506 665c255d 2023-08-04 jrmu (set-car! vals val))
507 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
508 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
509 665c255d 2023-08-04 jrmu (frame-values frame))))
511 665c255d 2023-08-04 jrmu ;; (define (remove-binding-from-frame! var frame)
512 665c255d 2023-08-04 jrmu ;; (define (scan vars vals)
513 665c255d 2023-08-04 jrmu ;; (cond ((null? (cdr vars))
514 665c255d 2023-08-04 jrmu ;; (error "Binding not found -- REMOVE-BINDING-FROM-FRAME!" var))
515 665c255d 2023-08-04 jrmu ;; ((eq? var (cadr vars))
516 665c255d 2023-08-04 jrmu ;; (set-cdr! vars (cddr vars))
517 665c255d 2023-08-04 jrmu ;; (set-cdr! vals (cddr vals)))
518 665c255d 2023-08-04 jrmu ;; (else (scan (cdr vars) (cdr vals)))))
519 665c255d 2023-08-04 jrmu ;; (let ((vars (frame-variables frame))
520 665c255d 2023-08-04 jrmu ;; (vals (frame-values frame)))
521 665c255d 2023-08-04 jrmu ;; (if (eq? var (car vars))
522 665c255d 2023-08-04 jrmu ;; (begin (set-car! frame (cdr vars))
523 665c255d 2023-08-04 jrmu ;; (set-cdr! frame (cdr vals)))
524 665c255d 2023-08-04 jrmu ;; (scan vars vals))))
526 665c255d 2023-08-04 jrmu ;; primitives
527 665c255d 2023-08-04 jrmu (define (primitive-procedure? proc)
528 665c255d 2023-08-04 jrmu (tagged-list? proc 'primitive))
529 665c255d 2023-08-04 jrmu (define (primitive-implementation proc) (cadr proc))
530 665c255d 2023-08-04 jrmu (define primitive-procedures
531 665c255d 2023-08-04 jrmu (list (list 'car car)
532 665c255d 2023-08-04 jrmu (list 'cdr cdr)
533 665c255d 2023-08-04 jrmu (list 'caar caar)
534 665c255d 2023-08-04 jrmu (list 'cadr cadr)
535 665c255d 2023-08-04 jrmu (list 'cddr cddr)
536 665c255d 2023-08-04 jrmu (list 'caddr caddr)
537 665c255d 2023-08-04 jrmu (list 'cdddr cdddr)
538 665c255d 2023-08-04 jrmu (list 'cons cons)
539 665c255d 2023-08-04 jrmu (list 'list list)
540 665c255d 2023-08-04 jrmu (list 'null? null?)
541 665c255d 2023-08-04 jrmu (list '* *)
542 665c255d 2023-08-04 jrmu (list '/ /)
543 665c255d 2023-08-04 jrmu (list '+ +)
544 665c255d 2023-08-04 jrmu (list '- -)
545 665c255d 2023-08-04 jrmu (list '= =)
546 665c255d 2023-08-04 jrmu (list '< <)
547 665c255d 2023-08-04 jrmu (list '> >)
548 665c255d 2023-08-04 jrmu (list '<= <=)
549 665c255d 2023-08-04 jrmu (list '>= >=)
550 665c255d 2023-08-04 jrmu (list 'abs abs)
551 665c255d 2023-08-04 jrmu (list 'remainder remainder)
552 665c255d 2023-08-04 jrmu (list 'eq? eq?)
553 665c255d 2023-08-04 jrmu (list 'equal? equal?)
554 665c255d 2023-08-04 jrmu (list 'member member)
555 665c255d 2023-08-04 jrmu (list 'display display)))
556 665c255d 2023-08-04 jrmu (define (primitive-procedure-names)
558 665c255d 2023-08-04 jrmu primitive-procedures))
559 665c255d 2023-08-04 jrmu (define (primitive-procedure-objects)
560 665c255d 2023-08-04 jrmu (map (lambda (proc) (list 'primitive (cadr proc)))
561 665c255d 2023-08-04 jrmu primitive-procedures))
562 665c255d 2023-08-04 jrmu (define (apply-primitive-procedure proc args)
564 665c255d 2023-08-04 jrmu (primitive-implementation proc) args))
566 665c255d 2023-08-04 jrmu ;; execute application
568 665c255d 2023-08-04 jrmu (define (execute-application proc args succeed fail)
569 665c255d 2023-08-04 jrmu (cond ((primitive-procedure? proc)
570 665c255d 2023-08-04 jrmu (succeed (apply-primitive-procedure proc args)
572 665c255d 2023-08-04 jrmu ((compound-procedure? proc)
573 665c255d 2023-08-04 jrmu ((procedure-body proc)
574 665c255d 2023-08-04 jrmu (extend-environment (procedure-parameters proc)
576 665c255d 2023-08-04 jrmu (procedure-environment proc))
581 665c255d 2023-08-04 jrmu "Unknown procedure type -- EXECUTE-APPLICATION"
585 665c255d 2023-08-04 jrmu ;; driver-loop
586 665c255d 2023-08-04 jrmu (define (prompt-for-input string)
587 665c255d 2023-08-04 jrmu (newline) (newline) (display string) (newline))
588 665c255d 2023-08-04 jrmu (define (announce-output string)
589 665c255d 2023-08-04 jrmu (newline) (display string) (newline))
590 665c255d 2023-08-04 jrmu (define (user-print object)
591 665c255d 2023-08-04 jrmu (if (compound-procedure? object)
592 665c255d 2023-08-04 jrmu (display (list 'compound-procedure
593 665c255d 2023-08-04 jrmu (procedure-parameters object)
594 665c255d 2023-08-04 jrmu (procedure-body object)
595 665c255d 2023-08-04 jrmu '<procedure-env>))
596 665c255d 2023-08-04 jrmu (display object)))
597 665c255d 2023-08-04 jrmu (define (setup-environment)
598 665c255d 2023-08-04 jrmu (let ((initial-env
599 665c255d 2023-08-04 jrmu (extend-environment (primitive-procedure-names)
600 665c255d 2023-08-04 jrmu (primitive-procedure-objects)
601 665c255d 2023-08-04 jrmu the-empty-environment)))
602 665c255d 2023-08-04 jrmu (define-variable! 'true true initial-env)
603 665c255d 2023-08-04 jrmu (define-variable! 'false false initial-env)
604 665c255d 2023-08-04 jrmu initial-env))
605 665c255d 2023-08-04 jrmu (define the-global-environment (setup-environment))
607 665c255d 2023-08-04 jrmu (define input-prompt ";;; Amb-Eval input:")
608 665c255d 2023-08-04 jrmu (define output-prompt ";;; Amb-Eval value:")
609 665c255d 2023-08-04 jrmu (define (driver-loop)
610 665c255d 2023-08-04 jrmu (define (internal-loop try-again)
611 665c255d 2023-08-04 jrmu (prompt-for-input input-prompt)
612 665c255d 2023-08-04 jrmu (let ((input (read)))
613 665c255d 2023-08-04 jrmu (if (eq? input 'try-again)
614 665c255d 2023-08-04 jrmu (try-again)
617 665c255d 2023-08-04 jrmu (display ";;; Starting a new problem ")
618 665c255d 2023-08-04 jrmu (ambeval input
619 665c255d 2023-08-04 jrmu the-global-environment
620 665c255d 2023-08-04 jrmu ;; ambeval success
621 665c255d 2023-08-04 jrmu (lambda (val next-alternative)
622 665c255d 2023-08-04 jrmu (announce-output output-prompt)
623 665c255d 2023-08-04 jrmu (user-print val)
624 665c255d 2023-08-04 jrmu (internal-loop next-alternative))
625 665c255d 2023-08-04 jrmu ;; ambeval failure
627 665c255d 2023-08-04 jrmu (announce-output
628 665c255d 2023-08-04 jrmu ";;; There are no more values of")
629 665c255d 2023-08-04 jrmu (user-print input)
630 665c255d 2023-08-04 jrmu (driver-loop)))))))
631 665c255d 2023-08-04 jrmu (internal-loop
634 665c255d 2023-08-04 jrmu (display ";;; There is no current problem")
635 665c255d 2023-08-04 jrmu (driver-loop))))
638 665c255d 2023-08-04 jrmu ;; auxiliary
639 665c255d 2023-08-04 jrmu (define (test-case actual expected)
641 665c255d 2023-08-04 jrmu (display "Actual: ")
642 665c255d 2023-08-04 jrmu (display actual)
644 665c255d 2023-08-04 jrmu (display "Expected: ")
645 665c255d 2023-08-04 jrmu (display expected)
647 665c255d 2023-08-04 jrmu (define try-again
649 665c255d 2023-08-04 jrmu "No current problem"))
650 665c255d 2023-08-04 jrmu (define (geval exp) ;; eval globally
651 665c255d 2023-08-04 jrmu (if (eq? exp 'try-again)
652 665c255d 2023-08-04 jrmu (try-again)
653 665c255d 2023-08-04 jrmu (ambeval exp
654 665c255d 2023-08-04 jrmu the-global-environment
655 665c255d 2023-08-04 jrmu (lambda (val next-alternative)
656 665c255d 2023-08-04 jrmu (set! try-again next-alternative)
659 665c255d 2023-08-04 jrmu (set! try-again
661 665c255d 2023-08-04 jrmu "No current problem"))
662 665c255d 2023-08-04 jrmu "No alternatives"))))
663 665c255d 2023-08-04 jrmu (define (test-eval exp expected)
664 665c255d 2023-08-04 jrmu (test-case (geval exp) expected))
667 665c255d 2023-08-04 jrmu ;; test-suite
669 665c255d 2023-08-04 jrmu ;; procedure definitions
672 665c255d 2023-08-04 jrmu '(define (assoc key records)
673 665c255d 2023-08-04 jrmu (cond ((null? records) false)
674 665c255d 2023-08-04 jrmu ((equal? key (caar records)) (car records))
675 665c255d 2023-08-04 jrmu (else (assoc key (cdr records))))))
678 665c255d 2023-08-04 jrmu '(define (map proc list)
679 665c255d 2023-08-04 jrmu (if (null? list)
681 665c255d 2023-08-04 jrmu (cons (proc (car list))
682 665c255d 2023-08-04 jrmu (map proc (cdr list))))))
685 665c255d 2023-08-04 jrmu '(define (accumulate op initial sequence)
686 665c255d 2023-08-04 jrmu (if (null? sequence)
688 665c255d 2023-08-04 jrmu (op (car sequence)
689 665c255d 2023-08-04 jrmu (accumulate op initial (cdr sequence))))))
691 665c255d 2023-08-04 jrmu ;; ;; all special forms
692 665c255d 2023-08-04 jrmu (test-eval '(begin 5 6) 6)
693 665c255d 2023-08-04 jrmu (test-eval '10 10)
694 665c255d 2023-08-04 jrmu (geval '(define x 3))
695 665c255d 2023-08-04 jrmu (test-eval 'x 3)
696 665c255d 2023-08-04 jrmu (test-eval '(set! x -25) 'ok)
697 665c255d 2023-08-04 jrmu (test-eval 'x -25)
698 665c255d 2023-08-04 jrmu (geval '(define z (lambda (x y) (+ x (* x y)))))
699 665c255d 2023-08-04 jrmu (test-eval '(z 3 4) 15)
700 665c255d 2023-08-04 jrmu (test-eval '(cond ((= x -2) 'x=-2)
701 665c255d 2023-08-04 jrmu ((= x -25) 'x=-25)
702 665c255d 2023-08-04 jrmu (else 'failed))
704 665c255d 2023-08-04 jrmu (test-eval '(if true false true) false)
707 665c255d 2023-08-04 jrmu '(let ((x 4) (y 7))
708 665c255d 2023-08-04 jrmu (+ x y (* x y)))
709 665c255d 2023-08-04 jrmu (+ 4 7 (* 4 7)))
713 665c255d 2023-08-04 jrmu (geval '(define x (+ 3 8)))
714 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x) 11)
715 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x false) false)
716 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x (set! x -2) false) false)
717 665c255d 2023-08-04 jrmu (test-eval 'x -2)
718 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x false (set! x -5)) false)
719 665c255d 2023-08-04 jrmu (test-eval 'x -2)
720 665c255d 2023-08-04 jrmu (test-eval '(or false (set! x 25)) 'ok)
721 665c255d 2023-08-04 jrmu (test-eval 'x 25)
722 665c255d 2023-08-04 jrmu (test-eval '(or (set! x 2) (set! x 4)) 'ok)
723 665c255d 2023-08-04 jrmu (test-eval 'x 2)
724 665c255d 2023-08-04 jrmu (test-eval '(or false (set! x 25) true false) 'ok)
725 665c255d 2023-08-04 jrmu (test-eval 'x 25)
726 665c255d 2023-08-04 jrmu (test-eval '(or ((lambda (x) x) 5)) 5)
727 665c255d 2023-08-04 jrmu (test-eval '(or (begin (set! x (+ x 1)) x)) 26) ;; this fails because or->if repeats the same clause twice
729 665c255d 2023-08-04 jrmu (display "Failure expected")
735 665c255d 2023-08-04 jrmu '(cond ((assoc 'b '((a 1) (b 2))) => cadr)
736 665c255d 2023-08-04 jrmu (else false))
740 665c255d 2023-08-04 jrmu '(cond ((= 3 4) 'not-true)
741 665c255d 2023-08-04 jrmu ((= (* 2 4) 3) 'also-false)
742 665c255d 2023-08-04 jrmu ((map (lambda (x)
743 665c255d 2023-08-04 jrmu (* x (+ x 1)))
744 665c255d 2023-08-04 jrmu '(2 4 1 9))
746 665c255d 2023-08-04 jrmu (lambda (x)
747 665c255d 2023-08-04 jrmu (accumulate + 0 x)))
748 665c255d 2023-08-04 jrmu (else 'never-reach))
750 665c255d 2023-08-04 jrmu ;; '(6 20 2 90)
753 665c255d 2023-08-04 jrmu ;; procedure definition and application
755 665c255d 2023-08-04 jrmu '(define (factorial n)
756 665c255d 2023-08-04 jrmu (if (= n 0)
758 665c255d 2023-08-04 jrmu (* n (factorial (- n 1))))))
759 665c255d 2023-08-04 jrmu (test-eval '(factorial 5) 120)
764 665c255d 2023-08-04 jrmu '(map (lambda (x)
765 665c255d 2023-08-04 jrmu (* x (+ x 1)))
766 665c255d 2023-08-04 jrmu '(2 1 4 2 8 3))
767 665c255d 2023-08-04 jrmu '(6 2 20 6 72 12))
768 665c255d 2023-08-04 jrmu ;; accumulate
771 665c255d 2023-08-04 jrmu '(accumulate + 0 '(1 2 3 4 5))
774 665c255d 2023-08-04 jrmu ;; make-let
776 665c255d 2023-08-04 jrmu (make-let '(x y) '(3 5) '((+ x y)))
783 665c255d 2023-08-04 jrmu '(let ((x 3))
787 665c255d 2023-08-04 jrmu '(let ((x 3)
792 665c255d 2023-08-04 jrmu '(let ((x 3)
794 665c255d 2023-08-04 jrmu (+ (let ((x (+ y 2))
798 665c255d 2023-08-04 jrmu (+ (* 4 3) 3 2))
800 665c255d 2023-08-04 jrmu '(let ((x 6)
801 665c255d 2023-08-04 jrmu (y (let ((x 2))
803 665c255d 2023-08-04 jrmu (z (let ((a (* 3 2)))
812 665c255d 2023-08-04 jrmu '(let* ((x 3)
813 665c255d 2023-08-04 jrmu (y (+ x 2))
814 665c255d 2023-08-04 jrmu (z (+ x y 5)))
823 665c255d 2023-08-04 jrmu '(let* ((x 3))
824 665c255d 2023-08-04 jrmu (let* ((y 5))
829 665c255d 2023-08-04 jrmu '(let* ((x 3)
830 665c255d 2023-08-04 jrmu (y (+ x 1)))
831 665c255d 2023-08-04 jrmu (+ (let* ((x (+ y 2))
835 665c255d 2023-08-04 jrmu (+ (* 6 6) 3 4))
837 665c255d 2023-08-04 jrmu '(let* ((x 6)
838 665c255d 2023-08-04 jrmu (y (let* ((x 2)
839 665c255d 2023-08-04 jrmu (a (let* ((x (* 3 x)))
842 665c255d 2023-08-04 jrmu (z (+ x y)))
846 665c255d 2023-08-04 jrmu ;; named-let
849 665c255d 2023-08-04 jrmu '(let eight ()
855 665c255d 2023-08-04 jrmu '(let loop ((count 0))
856 665c255d 2023-08-04 jrmu (if (= 100 count)
858 665c255d 2023-08-04 jrmu (loop (+ count 1))))
861 665c255d 2023-08-04 jrmu '(define (prime? x)
862 665c255d 2023-08-04 jrmu (let prime-iter ((i 2))
863 665c255d 2023-08-04 jrmu (cond ((> (* i i) x) true)
864 665c255d 2023-08-04 jrmu ((= (remainder x i) 0) false)
865 665c255d 2023-08-04 jrmu (else (prime-iter (+ i 1)))))))
867 665c255d 2023-08-04 jrmu '(let primes ((x 2)
869 665c255d 2023-08-04 jrmu (cond ((= n 0) '())
870 665c255d 2023-08-04 jrmu ((prime? x)
872 665c255d 2023-08-04 jrmu (primes (+ x 1) (- n 1))))
873 665c255d 2023-08-04 jrmu (else (primes (+ x 1) n))))
874 665c255d 2023-08-04 jrmu '(2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71))
877 665c255d 2023-08-04 jrmu '(define (fib n)
878 665c255d 2023-08-04 jrmu (let fib-iter ((a 1)
881 665c255d 2023-08-04 jrmu (if (= count 0)
883 665c255d 2023-08-04 jrmu (fib-iter (+ a b) a (- count 1))))))
884 665c255d 2023-08-04 jrmu (test-eval '(fib 19) 4181)
888 665c255d 2023-08-04 jrmu '(let ((y 0))
889 665c255d 2023-08-04 jrmu (do ((x 0 (+ x 1)))
890 665c255d 2023-08-04 jrmu ((= x 5) y)
891 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
902 665c255d 2023-08-04 jrmu '(let ((y 0))
904 665c255d 2023-08-04 jrmu ((= y 5) y)
905 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
909 665c255d 2023-08-04 jrmu '(do ((y '(1 2 3 4)))
910 665c255d 2023-08-04 jrmu ((null? y))
911 665c255d 2023-08-04 jrmu (set! y (cdr y)))
914 665c255d 2023-08-04 jrmu '(let ((y 0))
915 665c255d 2023-08-04 jrmu (do ((x 0 (+ x 1)))
916 665c255d 2023-08-04 jrmu ((= x 5) y)
917 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
920 665c255d 2023-08-04 jrmu '(let ((x '(1 3 5 7 9)))
921 665c255d 2023-08-04 jrmu (do ((x x (cdr x))
922 665c255d 2023-08-04 jrmu (sum 0 (+ sum (car x))))
923 665c255d 2023-08-04 jrmu ((null? x) sum)))
926 665c255d 2023-08-04 jrmu '(let ((z '()))
927 665c255d 2023-08-04 jrmu (do ((x '(1 2 3 4) (cdr x))
928 665c255d 2023-08-04 jrmu (y '(1 2 3 4 5 6 7 8) (cddr y)))
929 665c255d 2023-08-04 jrmu ((null? x) y x z)
930 665c255d 2023-08-04 jrmu (set! z (cons (car x) z))))
931 665c255d 2023-08-04 jrmu '(4 3 2 1))
935 665c255d 2023-08-04 jrmu ;; make-unbound!
936 665c255d 2023-08-04 jrmu ;; broken now due to scan-out-defines
938 665c255d 2023-08-04 jrmu ;; (test-eval
939 665c255d 2023-08-04 jrmu ;; '(let ((x 3))
940 665c255d 2023-08-04 jrmu ;; (let ((x 5))
941 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
942 665c255d 2023-08-04 jrmu ;; (* x x)))
945 665c255d 2023-08-04 jrmu ;; (test-eval
946 665c255d 2023-08-04 jrmu ;; '(let ((x 3))
947 665c255d 2023-08-04 jrmu ;; (let ((x 5))
948 665c255d 2023-08-04 jrmu ;; (define y x)
949 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
950 665c255d 2023-08-04 jrmu ;; (* y x)))
953 665c255d 2023-08-04 jrmu ;; (test-eval
954 665c255d 2023-08-04 jrmu ;; '(let ((y -1) (x 3))
955 665c255d 2023-08-04 jrmu ;; (let ((y 0.5) (x 5))
956 665c255d 2023-08-04 jrmu ;; (define a x)
957 665c255d 2023-08-04 jrmu ;; (define b y)
958 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
959 665c255d 2023-08-04 jrmu ;; (make-unbound! y)
960 665c255d 2023-08-04 jrmu ;; (* a b x y)))
961 665c255d 2023-08-04 jrmu ;; (* 5 3 -1 0.5))
963 665c255d 2023-08-04 jrmu ;; (test-eval
964 665c255d 2023-08-04 jrmu ;; '(let ((x 3) (y 4))
965 665c255d 2023-08-04 jrmu ;; (let ((x 5))
966 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
967 665c255d 2023-08-04 jrmu ;; (+ x 4)))
970 665c255d 2023-08-04 jrmu ;; (test-eval
971 665c255d 2023-08-04 jrmu ;; '(let ((a 1) (b 2) (c 3) (d 4))
972 665c255d 2023-08-04 jrmu ;; (make-unbound! b)
973 665c255d 2023-08-04 jrmu ;; (+ a c d))
974 665c255d 2023-08-04 jrmu ;; (+ 1 3 4))
976 665c255d 2023-08-04 jrmu ;; (test-eval
977 665c255d 2023-08-04 jrmu ;; '(let ((x 4) (y 5))
978 665c255d 2023-08-04 jrmu ;; (let ((a 1) (b 2) (c 3))
979 665c255d 2023-08-04 jrmu ;; (let ((x (+ a b)) (y (+ c a)))
980 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
981 665c255d 2023-08-04 jrmu ;; (let ((a x) (b (+ x y)))
982 665c255d 2023-08-04 jrmu ;; (define z b)
983 665c255d 2023-08-04 jrmu ;; (make-unbound! b)
984 665c255d 2023-08-04 jrmu ;; (* (+ a z)
985 665c255d 2023-08-04 jrmu ;; (+ a b y))))))
986 665c255d 2023-08-04 jrmu ;; (* (+ 4 8)
987 665c255d 2023-08-04 jrmu ;; (+ 4 2 4)))
989 665c255d 2023-08-04 jrmu ;; x 3 -- y 4
990 665c255d 2023-08-04 jrmu ;; x 4 -- y 4
991 665c255d 2023-08-04 jrmu ;; a 4 -- b 4
992 665c255d 2023-08-04 jrmu ;; a 4 -- b 2
994 665c255d 2023-08-04 jrmu ;; scan-out-defines
997 665c255d 2023-08-04 jrmu '(define (f x)
998 665c255d 2023-08-04 jrmu (define (even? n)
999 665c255d 2023-08-04 jrmu (if (= n 0)
1001 665c255d 2023-08-04 jrmu (odd? (- n 1))))
1002 665c255d 2023-08-04 jrmu (define (odd? n)
1003 665c255d 2023-08-04 jrmu (if (= n 0)
1005 665c255d 2023-08-04 jrmu (even? (- n 1))))
1006 665c255d 2023-08-04 jrmu (even? x)))
1007 665c255d 2023-08-04 jrmu (test-eval '(f 5) false)
1008 665c255d 2023-08-04 jrmu (test-eval '(f 10) true)
1010 665c255d 2023-08-04 jrmu ;; ;; (geval
1011 665c255d 2023-08-04 jrmu ;; ;; '(let ((x 5))
1012 665c255d 2023-08-04 jrmu ;; ;; (define y x)
1013 665c255d 2023-08-04 jrmu ;; ;; (define x 3)
1014 665c255d 2023-08-04 jrmu ;; ;; (+ x y)))
1015 665c255d 2023-08-04 jrmu ;; ;; signal an error because x is undefined if variables are scanned out
1017 665c255d 2023-08-04 jrmu ;; ;; letrec
1020 665c255d 2023-08-04 jrmu ;; '(define (f x)
1021 665c255d 2023-08-04 jrmu ;; (letrec ((even?
1022 665c255d 2023-08-04 jrmu ;; (lambda (n)
1023 665c255d 2023-08-04 jrmu ;; (if (= n 0)
1025 665c255d 2023-08-04 jrmu ;; (odd? (- n 1)))))
1027 665c255d 2023-08-04 jrmu ;; (lambda (n)
1028 665c255d 2023-08-04 jrmu ;; (if (= n 0)
1030 665c255d 2023-08-04 jrmu ;; (even? (- n 1))))))
1031 665c255d 2023-08-04 jrmu ;; (even? x))))
1032 665c255d 2023-08-04 jrmu ;; (test-eval '(f 11) false)
1033 665c255d 2023-08-04 jrmu ;; (test-eval '(f 16) true)
1035 665c255d 2023-08-04 jrmu ;; (test-eval
1036 665c255d 2023-08-04 jrmu ;; '(letrec ((fact
1037 665c255d 2023-08-04 jrmu ;; (lambda (n)
1038 665c255d 2023-08-04 jrmu ;; (if (= n 1)
1040 665c255d 2023-08-04 jrmu ;; (* n (fact (- n 1)))))))
1041 665c255d 2023-08-04 jrmu ;; (fact 10))
1042 665c255d 2023-08-04 jrmu ;; 3628800)
1045 665c255d 2023-08-04 jrmu (test-eval '(amb 1 2 3) 1)
1046 665c255d 2023-08-04 jrmu (test-eval 'try-again 2)
1047 665c255d 2023-08-04 jrmu (test-eval 'try-again 3)
1048 665c255d 2023-08-04 jrmu (test-eval 'try-again "No alternatives")
1049 665c255d 2023-08-04 jrmu (test-eval 'try-again "No current problem")
1050 665c255d 2023-08-04 jrmu (test-eval 'try-again "No current problem")
1051 665c255d 2023-08-04 jrmu (test-eval '(amb (amb 1 2) (amb 'a 'b))
1053 665c255d 2023-08-04 jrmu (test-eval 'try-again 2)
1054 665c255d 2023-08-04 jrmu (test-eval 'try-again 'a)
1055 665c255d 2023-08-04 jrmu (test-eval 'try-again 'b)
1056 665c255d 2023-08-04 jrmu (test-eval 'try-again "No alternatives")
1057 665c255d 2023-08-04 jrmu (geval '(define (require p) (if (not p) (amb))))
1058 665c255d 2023-08-04 jrmu (test-eval '(require false) "No alternatives")
1059 665c255d 2023-08-04 jrmu (test-eval '(require true) false)
1063 665c255d 2023-08-04 jrmu '(define (an-integer-between low high)
1064 665c255d 2023-08-04 jrmu (require (<= low high))
1065 665c255d 2023-08-04 jrmu (amb low (an-integer-between (+ low 1) high))))
1068 665c255d 2023-08-04 jrmu '(define (a-pythagorean-triple-between low high)
1069 665c255d 2023-08-04 jrmu (let ((i (an-integer-between low high)))
1070 665c255d 2023-08-04 jrmu (let ((j (an-integer-between i high)))
1071 665c255d 2023-08-04 jrmu (let ((k (an-integer-between j high)))
1072 665c255d 2023-08-04 jrmu (require (= (+ (* i i) (* j j)) (* k k)))
1073 665c255d 2023-08-04 jrmu (list i j k))))))
1075 665c255d 2023-08-04 jrmu ;; (test-eval
1076 665c255d 2023-08-04 jrmu ;; '(a-pythagorean-triple-between 1 20)
1077 665c255d 2023-08-04 jrmu ;; '(3 4 5))
1078 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(5 12 13))
1079 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(6 8 10))
1080 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(8 15 17))
1081 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(9 12 15))
1084 665c255d 2023-08-04 jrmu '(define (an-integer-starting-from low)
1085 665c255d 2023-08-04 jrmu (amb low (an-integer-starting-from (+ low 1)))))
1088 665c255d 2023-08-04 jrmu '(define (pythagorean-triples-starting-from low)
1089 665c255d 2023-08-04 jrmu (let* ((k (an-integer-starting-from low))
1090 665c255d 2023-08-04 jrmu (i (an-integer-between low k))
1091 665c255d 2023-08-04 jrmu (j (an-integer-between i k)))
1092 665c255d 2023-08-04 jrmu (require (= (+ (* i i) (* j j)) (* k k)))
1093 665c255d 2023-08-04 jrmu (list i j k))))
1095 665c255d 2023-08-04 jrmu ;; (test-eval '(pythagorean-triples-starting-from 1)
1096 665c255d 2023-08-04 jrmu ;; '(3 4 5))
1097 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(6 8 10))
1098 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(5 12 13))
1099 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(9 12 15))
1100 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(8 15 17))
1103 665c255d 2023-08-04 jrmu '(define (next-triplet trp)
1104 665c255d 2023-08-04 jrmu (let ((i (car trp))
1105 665c255d 2023-08-04 jrmu (j (cadr trp))
1106 665c255d 2023-08-04 jrmu (k (caddr trp)))
1107 665c255d 2023-08-04 jrmu (cond ((= i j k) (list 1 1 (+ k 1)))
1108 665c255d 2023-08-04 jrmu ((= j k) (list (+ i 1) (+ i 1) k))
1109 665c255d 2023-08-04 jrmu (else (list i (+ j 1) k))))))
1111 665c255d 2023-08-04 jrmu '(define (triplet-starting-from trp)
1112 665c255d 2023-08-04 jrmu (amb trp (triplet-starting-from (next-triplet trp)))))
1114 665c255d 2023-08-04 jrmu '(define (pythagorean-triples-starting-from low)
1115 665c255d 2023-08-04 jrmu (let* ((triplet (triplet-starting-from (list low low low)))
1116 665c255d 2023-08-04 jrmu (i (car triplet))
1117 665c255d 2023-08-04 jrmu (j (cadr triplet))
1118 665c255d 2023-08-04 jrmu (k (caddr triplet)))
1119 665c255d 2023-08-04 jrmu (require (= (+ (* i i) (* j j)) (* k k)))
1120 665c255d 2023-08-04 jrmu (list i j k))))
1122 665c255d 2023-08-04 jrmu '(define (distinct? items)
1123 665c255d 2023-08-04 jrmu (cond ((null? items) true)
1124 665c255d 2023-08-04 jrmu ((null? (cdr items)) true)
1125 665c255d 2023-08-04 jrmu ((member (car items) (cdr items)) false)
1126 665c255d 2023-08-04 jrmu (else (distinct? (cdr items))))))
1129 665c255d 2023-08-04 jrmu ;; Exercise 4.44. Exercise 2.42 described the ``eight-queens puzzle'' of placing queens on a chessboard so that no two attack each other. Write a nondeterministic program to solve this puzzle.
1131 665c255d 2023-08-04 jrmu (define (queens queen-positions n)
1132 665c255d 2023-08-04 jrmu (if (= (length queen-positions) n)
1133 665c255d 2023-08-04 jrmu queen-positions
1134 665c255d 2023-08-04 jrmu (let ((new-position (amb 1 2 3 4 5 6 7 8)))
1135 665c255d 2023-08-04 jrmu (require (new-position
1136 665c255d 2023-08-04 jrmu (queens (append new-position queen-positions) n)
1138 665c255d 2023-08-04 jrmu (define (safe? col positions)
1139 665c255d 2023-08-04 jrmu (define (exclude-last list)
1140 665c255d 2023-08-04 jrmu (cond ((null? list) (error "empty list"))
1141 665c255d 2023-08-04 jrmu ((null? (cdr list)) '())
1142 665c255d 2023-08-04 jrmu (else (cons (car list) (exclude-last (cdr list))))))
1143 665c255d 2023-08-04 jrmu (let ((row (list-ref positions (- col 1)))
1144 665c255d 2023-08-04 jrmu (all-but-last (exclude-last positions)))
1145 665c255d 2023-08-04 jrmu (let ((same-row?
1146 665c255d 2023-08-04 jrmu (fold-left (lambda (result next-row)
1147 665c255d 2023-08-04 jrmu (or result
1148 665c255d 2023-08-04 jrmu (= next-row row)))
1150 665c255d 2023-08-04 jrmu all-but-last))
1151 665c255d 2023-08-04 jrmu (same-positive-diagonal?
1152 665c255d 2023-08-04 jrmu (fold-left (lambda (result row-col-sum)
1153 665c255d 2023-08-04 jrmu (or result
1154 665c255d 2023-08-04 jrmu (= (+ row col) row-col-sum)))
1156 665c255d 2023-08-04 jrmu (map + all-but-last (enumerate-interval 1 (- col 1)))))
1157 665c255d 2023-08-04 jrmu (same-negative-diagonal?
1158 665c255d 2023-08-04 jrmu (fold-left (lambda (result row-col-dif)
1159 665c255d 2023-08-04 jrmu (or result
1160 665c255d 2023-08-04 jrmu (= (- row col) row-col-dif)))
1162 665c255d 2023-08-04 jrmu (map - all-but-last (enumerate-interval 1 (- col 1))))))
1163 665c255d 2023-08-04 jrmu (not (or same-row? same-positive-diagonal? same-negative-diagonal?)))))
