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 (car vals))
480 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
481 665c255d 2023-08-04 jrmu (if (eq? env the-empty-environment)
482 665c255d 2023-08-04 jrmu (error "Unbound variable" var)
483 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
484 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
485 665c255d 2023-08-04 jrmu (frame-values frame)))))
486 665c255d 2023-08-04 jrmu (env-loop env))
487 665c255d 2023-08-04 jrmu (define (set-variable-value! var val env)
488 665c255d 2023-08-04 jrmu (define (env-loop env)
489 665c255d 2023-08-04 jrmu (define (scan vars vals)
490 665c255d 2023-08-04 jrmu (cond ((null? vars)
491 665c255d 2023-08-04 jrmu (env-loop (enclosing-environment env)))
492 665c255d 2023-08-04 jrmu ((eq? var (car vars))
493 665c255d 2023-08-04 jrmu (set-car! vals val))
494 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
495 665c255d 2023-08-04 jrmu (if (eq? env the-empty-environment)
496 665c255d 2023-08-04 jrmu (error "Unbound variable -- SET!" var)
497 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
498 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
499 665c255d 2023-08-04 jrmu (frame-values frame)))))
500 665c255d 2023-08-04 jrmu (env-loop env))
501 665c255d 2023-08-04 jrmu (define (define-variable! var val env)
502 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
503 665c255d 2023-08-04 jrmu (define (scan vars vals)
504 665c255d 2023-08-04 jrmu (cond ((null? vars)
505 665c255d 2023-08-04 jrmu (add-binding-to-frame! var val frame))
506 665c255d 2023-08-04 jrmu ((eq? var (car vars))
507 665c255d 2023-08-04 jrmu (set-car! vals val))
508 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
509 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
510 665c255d 2023-08-04 jrmu (frame-values frame))))
512 665c255d 2023-08-04 jrmu ;; (define (remove-binding-from-frame! var frame)
513 665c255d 2023-08-04 jrmu ;; (define (scan vars vals)
514 665c255d 2023-08-04 jrmu ;; (cond ((null? (cdr vars))
515 665c255d 2023-08-04 jrmu ;; (error "Binding not found -- REMOVE-BINDING-FROM-FRAME!" var))
516 665c255d 2023-08-04 jrmu ;; ((eq? var (cadr vars))
517 665c255d 2023-08-04 jrmu ;; (set-cdr! vars (cddr vars))
518 665c255d 2023-08-04 jrmu ;; (set-cdr! vals (cddr vals)))
519 665c255d 2023-08-04 jrmu ;; (else (scan (cdr vars) (cdr vals)))))
520 665c255d 2023-08-04 jrmu ;; (let ((vars (frame-variables frame))
521 665c255d 2023-08-04 jrmu ;; (vals (frame-values frame)))
522 665c255d 2023-08-04 jrmu ;; (if (eq? var (car vars))
523 665c255d 2023-08-04 jrmu ;; (begin (set-car! frame (cdr vars))
524 665c255d 2023-08-04 jrmu ;; (set-cdr! frame (cdr vals)))
525 665c255d 2023-08-04 jrmu ;; (scan vars vals))))
527 665c255d 2023-08-04 jrmu ;; primitives
528 665c255d 2023-08-04 jrmu (define (primitive-procedure? proc)
529 665c255d 2023-08-04 jrmu (tagged-list? proc 'primitive))
530 665c255d 2023-08-04 jrmu (define (primitive-implementation proc) (cadr proc))
531 665c255d 2023-08-04 jrmu (define primitive-procedures
532 665c255d 2023-08-04 jrmu (list (list 'car car)
533 665c255d 2023-08-04 jrmu (list 'cdr cdr)
534 665c255d 2023-08-04 jrmu (list 'caar caar)
535 665c255d 2023-08-04 jrmu (list 'cadr cadr)
536 665c255d 2023-08-04 jrmu (list 'cddr cddr)
537 665c255d 2023-08-04 jrmu (list 'caddr caddr)
538 665c255d 2023-08-04 jrmu (list 'cdddr cdddr)
539 665c255d 2023-08-04 jrmu (list 'cons cons)
540 665c255d 2023-08-04 jrmu (list 'list list)
541 665c255d 2023-08-04 jrmu (list 'null? null?)
542 665c255d 2023-08-04 jrmu (list 'pair? pair?)
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 '<= <=)
551 665c255d 2023-08-04 jrmu (list '>= >=)
552 665c255d 2023-08-04 jrmu (list 'abs abs)
553 665c255d 2023-08-04 jrmu (list 'remainder remainder)
554 665c255d 2023-08-04 jrmu (list 'eq? eq?)
555 665c255d 2023-08-04 jrmu (list 'equal? equal?)
556 665c255d 2023-08-04 jrmu (list 'member member)
557 665c255d 2023-08-04 jrmu (list 'display display)
558 665c255d 2023-08-04 jrmu (list 'error error)))
559 665c255d 2023-08-04 jrmu (define (primitive-procedure-names)
561 665c255d 2023-08-04 jrmu primitive-procedures))
562 665c255d 2023-08-04 jrmu (define (primitive-procedure-objects)
563 665c255d 2023-08-04 jrmu (map (lambda (proc) (list 'primitive (cadr proc)))
564 665c255d 2023-08-04 jrmu primitive-procedures))
565 665c255d 2023-08-04 jrmu (define (apply-primitive-procedure proc args)
567 665c255d 2023-08-04 jrmu (primitive-implementation proc) args))
569 665c255d 2023-08-04 jrmu ;; execute application
571 665c255d 2023-08-04 jrmu (define (execute-application proc args succeed fail)
572 665c255d 2023-08-04 jrmu (cond ((primitive-procedure? proc)
573 665c255d 2023-08-04 jrmu (succeed (apply-primitive-procedure proc args)
575 665c255d 2023-08-04 jrmu ((compound-procedure? proc)
576 665c255d 2023-08-04 jrmu ((procedure-body proc)
577 665c255d 2023-08-04 jrmu (extend-environment (procedure-parameters proc)
579 665c255d 2023-08-04 jrmu (procedure-environment proc))
584 665c255d 2023-08-04 jrmu "Unknown procedure type -- EXECUTE-APPLICATION"
588 665c255d 2023-08-04 jrmu ;; driver-loop
589 665c255d 2023-08-04 jrmu (define (prompt-for-input string)
590 665c255d 2023-08-04 jrmu (newline) (newline) (display string) (newline))
591 665c255d 2023-08-04 jrmu (define (announce-output string)
592 665c255d 2023-08-04 jrmu (newline) (display string) (newline))
593 665c255d 2023-08-04 jrmu (define (user-print object)
594 665c255d 2023-08-04 jrmu (if (compound-procedure? object)
595 665c255d 2023-08-04 jrmu (display (list 'compound-procedure
596 665c255d 2023-08-04 jrmu (procedure-parameters object)
597 665c255d 2023-08-04 jrmu (procedure-body object)
598 665c255d 2023-08-04 jrmu '<procedure-env>))
599 665c255d 2023-08-04 jrmu (display object)))
600 665c255d 2023-08-04 jrmu (define (setup-environment)
601 665c255d 2023-08-04 jrmu (let ((initial-env
602 665c255d 2023-08-04 jrmu (extend-environment (primitive-procedure-names)
603 665c255d 2023-08-04 jrmu (primitive-procedure-objects)
604 665c255d 2023-08-04 jrmu the-empty-environment)))
605 665c255d 2023-08-04 jrmu (define-variable! 'true true initial-env)
606 665c255d 2023-08-04 jrmu (define-variable! 'false false initial-env)
607 665c255d 2023-08-04 jrmu initial-env))
608 665c255d 2023-08-04 jrmu (define the-global-environment (setup-environment))
610 665c255d 2023-08-04 jrmu (define input-prompt ";;; Amb-Eval input:")
611 665c255d 2023-08-04 jrmu (define output-prompt ";;; Amb-Eval value:")
612 665c255d 2023-08-04 jrmu (define (driver-loop)
613 665c255d 2023-08-04 jrmu (define (internal-loop try-again)
614 665c255d 2023-08-04 jrmu (prompt-for-input input-prompt)
615 665c255d 2023-08-04 jrmu (let ((input (read)))
616 665c255d 2023-08-04 jrmu (if (eq? input 'try-again)
617 665c255d 2023-08-04 jrmu (try-again)
620 665c255d 2023-08-04 jrmu (display ";;; Starting a new problem ")
621 665c255d 2023-08-04 jrmu (ambeval input
622 665c255d 2023-08-04 jrmu the-global-environment
623 665c255d 2023-08-04 jrmu ;; ambeval success
624 665c255d 2023-08-04 jrmu (lambda (val next-alternative)
625 665c255d 2023-08-04 jrmu (announce-output output-prompt)
626 665c255d 2023-08-04 jrmu (user-print val)
627 665c255d 2023-08-04 jrmu (internal-loop next-alternative))
628 665c255d 2023-08-04 jrmu ;; ambeval failure
630 665c255d 2023-08-04 jrmu (announce-output
631 665c255d 2023-08-04 jrmu ";;; There are no more values of")
632 665c255d 2023-08-04 jrmu (user-print input)
633 665c255d 2023-08-04 jrmu (driver-loop)))))))
634 665c255d 2023-08-04 jrmu (internal-loop
637 665c255d 2023-08-04 jrmu (display ";;; There is no current problem")
638 665c255d 2023-08-04 jrmu (driver-loop))))
641 665c255d 2023-08-04 jrmu ;; auxiliary
642 665c255d 2023-08-04 jrmu (define (test-case actual expected)
644 665c255d 2023-08-04 jrmu (display "Actual: ")
645 665c255d 2023-08-04 jrmu (display actual)
647 665c255d 2023-08-04 jrmu (display "Expected: ")
648 665c255d 2023-08-04 jrmu (display expected)
650 665c255d 2023-08-04 jrmu (define try-again
652 665c255d 2023-08-04 jrmu "No current problem"))
653 665c255d 2023-08-04 jrmu (define (geval exp) ;; eval globally
654 665c255d 2023-08-04 jrmu (if (eq? exp 'try-again)
655 665c255d 2023-08-04 jrmu (try-again)
656 665c255d 2023-08-04 jrmu (ambeval exp
657 665c255d 2023-08-04 jrmu the-global-environment
658 665c255d 2023-08-04 jrmu (lambda (val next-alternative)
659 665c255d 2023-08-04 jrmu (set! try-again next-alternative)
662 665c255d 2023-08-04 jrmu (set! try-again
664 665c255d 2023-08-04 jrmu "No current problem"))
665 665c255d 2023-08-04 jrmu "No alternatives"))))
666 665c255d 2023-08-04 jrmu (define (test-eval exp expected)
667 665c255d 2023-08-04 jrmu (test-case (geval exp) expected))
670 665c255d 2023-08-04 jrmu ;; test-suite
672 665c255d 2023-08-04 jrmu ;; procedure definitions
675 665c255d 2023-08-04 jrmu '(define (append x y)
676 665c255d 2023-08-04 jrmu (if (null? x)
678 665c255d 2023-08-04 jrmu (cons (car x) (append (cdr x) y)))))
680 665c255d 2023-08-04 jrmu '(define (list-ref items n)
681 665c255d 2023-08-04 jrmu (if (= n 0)
682 665c255d 2023-08-04 jrmu (car items)
683 665c255d 2023-08-04 jrmu (list-ref (cdr items) (- n 1)))))
685 665c255d 2023-08-04 jrmu '(define (fold-left f init seq)
686 665c255d 2023-08-04 jrmu (if (null? seq)
688 665c255d 2023-08-04 jrmu (fold-left f
689 665c255d 2023-08-04 jrmu (f init (car seq))
690 665c255d 2023-08-04 jrmu (cdr seq)))))
692 665c255d 2023-08-04 jrmu '(define (enumerate-interval low high)
693 665c255d 2023-08-04 jrmu (if (> low high)
695 665c255d 2023-08-04 jrmu (cons low (enumerate-interval (+ low 1) high)))))
697 665c255d 2023-08-04 jrmu '(define (assoc key records)
698 665c255d 2023-08-04 jrmu (cond ((null? records) false)
699 665c255d 2023-08-04 jrmu ((equal? key (caar records)) (car records))
700 665c255d 2023-08-04 jrmu (else (assoc key (cdr records))))))
703 665c255d 2023-08-04 jrmu '(define (map proc list)
704 665c255d 2023-08-04 jrmu (if (null? list)
706 665c255d 2023-08-04 jrmu (cons (proc (car list))
707 665c255d 2023-08-04 jrmu (map proc (cdr list))))))
709 665c255d 2023-08-04 jrmu '(define (map-2 proc l1 l2)
710 665c255d 2023-08-04 jrmu (if (null? l1)
712 665c255d 2023-08-04 jrmu (cons (proc (car l1) (car l2))
713 665c255d 2023-08-04 jrmu (map-2 proc (cdr l1) (cdr l2))))))
716 665c255d 2023-08-04 jrmu '(define (accumulate op initial sequence)
717 665c255d 2023-08-04 jrmu (if (null? sequence)
719 665c255d 2023-08-04 jrmu (op (car sequence)
720 665c255d 2023-08-04 jrmu (accumulate op initial (cdr sequence))))))
722 665c255d 2023-08-04 jrmu ;; ;; all special forms
723 665c255d 2023-08-04 jrmu (test-eval '(begin 5 6) 6)
724 665c255d 2023-08-04 jrmu (test-eval '10 10)
725 665c255d 2023-08-04 jrmu (geval '(define x 3))
726 665c255d 2023-08-04 jrmu (test-eval 'x 3)
727 665c255d 2023-08-04 jrmu (test-eval '(set! x -25) 'ok)
728 665c255d 2023-08-04 jrmu (test-eval 'x -25)
729 665c255d 2023-08-04 jrmu (geval '(define z (lambda (x y) (+ x (* x y)))))
730 665c255d 2023-08-04 jrmu (test-eval '(z 3 4) 15)
731 665c255d 2023-08-04 jrmu (test-eval '(cond ((= x -2) 'x=-2)
732 665c255d 2023-08-04 jrmu ((= x -25) 'x=-25)
733 665c255d 2023-08-04 jrmu (else 'failed))
735 665c255d 2023-08-04 jrmu (test-eval '(if true false true) false)
738 665c255d 2023-08-04 jrmu '(let ((x 4) (y 7))
739 665c255d 2023-08-04 jrmu (+ x y (* x y)))
740 665c255d 2023-08-04 jrmu (+ 4 7 (* 4 7)))
744 665c255d 2023-08-04 jrmu (geval '(define x (+ 3 8)))
745 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x) 11)
746 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x false) false)
747 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x (set! x -2) false) false)
748 665c255d 2023-08-04 jrmu (test-eval 'x -2)
749 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x false (set! x -5)) false)
750 665c255d 2023-08-04 jrmu (test-eval 'x -2)
751 665c255d 2023-08-04 jrmu (test-eval '(or false (set! x 25)) 'ok)
752 665c255d 2023-08-04 jrmu (test-eval 'x 25)
753 665c255d 2023-08-04 jrmu (test-eval '(or (set! x 2) (set! x 4)) 'ok)
754 665c255d 2023-08-04 jrmu (test-eval 'x 2)
755 665c255d 2023-08-04 jrmu (test-eval '(or false (set! x 25) true false) 'ok)
756 665c255d 2023-08-04 jrmu (test-eval 'x 25)
757 665c255d 2023-08-04 jrmu (test-eval '(or ((lambda (x) x) 5)) 5)
758 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
760 665c255d 2023-08-04 jrmu (display "Failure expected")
766 665c255d 2023-08-04 jrmu '(cond ((assoc 'b '((a 1) (b 2))) => cadr)
767 665c255d 2023-08-04 jrmu (else false))
771 665c255d 2023-08-04 jrmu '(cond ((= 3 4) 'not-true)
772 665c255d 2023-08-04 jrmu ((= (* 2 4) 3) 'also-false)
773 665c255d 2023-08-04 jrmu ((map (lambda (x)
774 665c255d 2023-08-04 jrmu (* x (+ x 1)))
775 665c255d 2023-08-04 jrmu '(2 4 1 9))
777 665c255d 2023-08-04 jrmu (lambda (x)
778 665c255d 2023-08-04 jrmu (accumulate + 0 x)))
779 665c255d 2023-08-04 jrmu (else 'never-reach))
781 665c255d 2023-08-04 jrmu ;; '(6 20 2 90)
784 665c255d 2023-08-04 jrmu ;; procedure definition and application
786 665c255d 2023-08-04 jrmu '(define (factorial n)
787 665c255d 2023-08-04 jrmu (if (= n 0)
789 665c255d 2023-08-04 jrmu (* n (factorial (- n 1))))))
790 665c255d 2023-08-04 jrmu (test-eval '(factorial 5) 120)
795 665c255d 2023-08-04 jrmu '(map (lambda (x)
796 665c255d 2023-08-04 jrmu (* x (+ x 1)))
797 665c255d 2023-08-04 jrmu '(2 1 4 2 8 3))
798 665c255d 2023-08-04 jrmu '(6 2 20 6 72 12))
799 665c255d 2023-08-04 jrmu ;; accumulate
802 665c255d 2023-08-04 jrmu '(accumulate + 0 '(1 2 3 4 5))
805 665c255d 2023-08-04 jrmu ;; make-let
807 665c255d 2023-08-04 jrmu (make-let '(x y) '(3 5) '((+ x y)))
814 665c255d 2023-08-04 jrmu '(let ((x 3))
818 665c255d 2023-08-04 jrmu '(let ((x 3)
823 665c255d 2023-08-04 jrmu '(let ((x 3)
825 665c255d 2023-08-04 jrmu (+ (let ((x (+ y 2))
829 665c255d 2023-08-04 jrmu (+ (* 4 3) 3 2))
831 665c255d 2023-08-04 jrmu '(let ((x 6)
832 665c255d 2023-08-04 jrmu (y (let ((x 2))
834 665c255d 2023-08-04 jrmu (z (let ((a (* 3 2)))
843 665c255d 2023-08-04 jrmu '(let* ((x 3)
844 665c255d 2023-08-04 jrmu (y (+ x 2))
845 665c255d 2023-08-04 jrmu (z (+ x y 5)))
854 665c255d 2023-08-04 jrmu '(let* ((x 3))
855 665c255d 2023-08-04 jrmu (let* ((y 5))
860 665c255d 2023-08-04 jrmu '(let* ((x 3)
861 665c255d 2023-08-04 jrmu (y (+ x 1)))
862 665c255d 2023-08-04 jrmu (+ (let* ((x (+ y 2))
866 665c255d 2023-08-04 jrmu (+ (* 6 6) 3 4))
868 665c255d 2023-08-04 jrmu '(let* ((x 6)
869 665c255d 2023-08-04 jrmu (y (let* ((x 2)
870 665c255d 2023-08-04 jrmu (a (let* ((x (* 3 x)))
873 665c255d 2023-08-04 jrmu (z (+ x y)))
877 665c255d 2023-08-04 jrmu ;; named-let
880 665c255d 2023-08-04 jrmu '(let eight ()
886 665c255d 2023-08-04 jrmu '(let loop ((count 0))
887 665c255d 2023-08-04 jrmu (if (= 100 count)
889 665c255d 2023-08-04 jrmu (loop (+ count 1))))
892 665c255d 2023-08-04 jrmu '(define (prime? x)
893 665c255d 2023-08-04 jrmu (let prime-iter ((i 2))
894 665c255d 2023-08-04 jrmu (cond ((> (* i i) x) true)
895 665c255d 2023-08-04 jrmu ((= (remainder x i) 0) false)
896 665c255d 2023-08-04 jrmu (else (prime-iter (+ i 1)))))))
898 665c255d 2023-08-04 jrmu '(let primes ((x 2)
900 665c255d 2023-08-04 jrmu (cond ((= n 0) '())
901 665c255d 2023-08-04 jrmu ((prime? x)
903 665c255d 2023-08-04 jrmu (primes (+ x 1) (- n 1))))
904 665c255d 2023-08-04 jrmu (else (primes (+ x 1) n))))
905 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))
908 665c255d 2023-08-04 jrmu '(define (fib n)
909 665c255d 2023-08-04 jrmu (let fib-iter ((a 1)
912 665c255d 2023-08-04 jrmu (if (= count 0)
914 665c255d 2023-08-04 jrmu (fib-iter (+ a b) a (- count 1))))))
915 665c255d 2023-08-04 jrmu (test-eval '(fib 19) 4181)
919 665c255d 2023-08-04 jrmu '(let ((y 0))
920 665c255d 2023-08-04 jrmu (do ((x 0 (+ x 1)))
921 665c255d 2023-08-04 jrmu ((= x 5) y)
922 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
933 665c255d 2023-08-04 jrmu '(let ((y 0))
935 665c255d 2023-08-04 jrmu ((= y 5) y)
936 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
940 665c255d 2023-08-04 jrmu '(do ((y '(1 2 3 4)))
941 665c255d 2023-08-04 jrmu ((null? y))
942 665c255d 2023-08-04 jrmu (set! y (cdr y)))
945 665c255d 2023-08-04 jrmu '(let ((y 0))
946 665c255d 2023-08-04 jrmu (do ((x 0 (+ x 1)))
947 665c255d 2023-08-04 jrmu ((= x 5) y)
948 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
951 665c255d 2023-08-04 jrmu '(let ((x '(1 3 5 7 9)))
952 665c255d 2023-08-04 jrmu (do ((x x (cdr x))
953 665c255d 2023-08-04 jrmu (sum 0 (+ sum (car x))))
954 665c255d 2023-08-04 jrmu ((null? x) sum)))
957 665c255d 2023-08-04 jrmu '(let ((z '()))
958 665c255d 2023-08-04 jrmu (do ((x '(1 2 3 4) (cdr x))
959 665c255d 2023-08-04 jrmu (y '(1 2 3 4 5 6 7 8) (cddr y)))
960 665c255d 2023-08-04 jrmu ((null? x) y x z)
961 665c255d 2023-08-04 jrmu (set! z (cons (car x) z))))
962 665c255d 2023-08-04 jrmu '(4 3 2 1))
966 665c255d 2023-08-04 jrmu ;; make-unbound!
967 665c255d 2023-08-04 jrmu ;; broken now due to scan-out-defines
969 665c255d 2023-08-04 jrmu ;; (test-eval
970 665c255d 2023-08-04 jrmu ;; '(let ((x 3))
971 665c255d 2023-08-04 jrmu ;; (let ((x 5))
972 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
973 665c255d 2023-08-04 jrmu ;; (* x x)))
976 665c255d 2023-08-04 jrmu ;; (test-eval
977 665c255d 2023-08-04 jrmu ;; '(let ((x 3))
978 665c255d 2023-08-04 jrmu ;; (let ((x 5))
979 665c255d 2023-08-04 jrmu ;; (define y x)
980 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
981 665c255d 2023-08-04 jrmu ;; (* y x)))
984 665c255d 2023-08-04 jrmu ;; (test-eval
985 665c255d 2023-08-04 jrmu ;; '(let ((y -1) (x 3))
986 665c255d 2023-08-04 jrmu ;; (let ((y 0.5) (x 5))
987 665c255d 2023-08-04 jrmu ;; (define a x)
988 665c255d 2023-08-04 jrmu ;; (define b y)
989 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
990 665c255d 2023-08-04 jrmu ;; (make-unbound! y)
991 665c255d 2023-08-04 jrmu ;; (* a b x y)))
992 665c255d 2023-08-04 jrmu ;; (* 5 3 -1 0.5))
994 665c255d 2023-08-04 jrmu ;; (test-eval
995 665c255d 2023-08-04 jrmu ;; '(let ((x 3) (y 4))
996 665c255d 2023-08-04 jrmu ;; (let ((x 5))
997 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
998 665c255d 2023-08-04 jrmu ;; (+ x 4)))
1001 665c255d 2023-08-04 jrmu ;; (test-eval
1002 665c255d 2023-08-04 jrmu ;; '(let ((a 1) (b 2) (c 3) (d 4))
1003 665c255d 2023-08-04 jrmu ;; (make-unbound! b)
1004 665c255d 2023-08-04 jrmu ;; (+ a c d))
1005 665c255d 2023-08-04 jrmu ;; (+ 1 3 4))
1007 665c255d 2023-08-04 jrmu ;; (test-eval
1008 665c255d 2023-08-04 jrmu ;; '(let ((x 4) (y 5))
1009 665c255d 2023-08-04 jrmu ;; (let ((a 1) (b 2) (c 3))
1010 665c255d 2023-08-04 jrmu ;; (let ((x (+ a b)) (y (+ c a)))
1011 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
1012 665c255d 2023-08-04 jrmu ;; (let ((a x) (b (+ x y)))
1013 665c255d 2023-08-04 jrmu ;; (define z b)
1014 665c255d 2023-08-04 jrmu ;; (make-unbound! b)
1015 665c255d 2023-08-04 jrmu ;; (* (+ a z)
1016 665c255d 2023-08-04 jrmu ;; (+ a b y))))))
1017 665c255d 2023-08-04 jrmu ;; (* (+ 4 8)
1018 665c255d 2023-08-04 jrmu ;; (+ 4 2 4)))
1020 665c255d 2023-08-04 jrmu ;; x 3 -- y 4
1021 665c255d 2023-08-04 jrmu ;; x 4 -- y 4
1022 665c255d 2023-08-04 jrmu ;; a 4 -- b 4
1023 665c255d 2023-08-04 jrmu ;; a 4 -- b 2
1025 665c255d 2023-08-04 jrmu ;; scan-out-defines
1028 665c255d 2023-08-04 jrmu '(define (f x)
1029 665c255d 2023-08-04 jrmu (define (even? n)
1030 665c255d 2023-08-04 jrmu (if (= n 0)
1032 665c255d 2023-08-04 jrmu (odd? (- n 1))))
1033 665c255d 2023-08-04 jrmu (define (odd? n)
1034 665c255d 2023-08-04 jrmu (if (= n 0)
1036 665c255d 2023-08-04 jrmu (even? (- n 1))))
1037 665c255d 2023-08-04 jrmu (even? x)))
1038 665c255d 2023-08-04 jrmu (test-eval '(f 5) false)
1039 665c255d 2023-08-04 jrmu (test-eval '(f 10) true)
1042 665c255d 2023-08-04 jrmu ;; '(let ((x 5))
1043 665c255d 2023-08-04 jrmu ;; (define y x)
1044 665c255d 2023-08-04 jrmu ;; (define x 3)
1045 665c255d 2023-08-04 jrmu ;; (+ x y)))
1046 665c255d 2023-08-04 jrmu ;; signal an error because x is undefined if variables are scanned out
1051 665c255d 2023-08-04 jrmu '(define (f x)
1052 665c255d 2023-08-04 jrmu (letrec ((even?
1053 665c255d 2023-08-04 jrmu (lambda (n)
1054 665c255d 2023-08-04 jrmu (if (= n 0)
1056 665c255d 2023-08-04 jrmu (odd? (- n 1)))))
1058 665c255d 2023-08-04 jrmu (lambda (n)
1059 665c255d 2023-08-04 jrmu (if (= n 0)
1061 665c255d 2023-08-04 jrmu (even? (- n 1))))))
1062 665c255d 2023-08-04 jrmu (even? x))))
1063 665c255d 2023-08-04 jrmu (test-eval '(f 11) false)
1064 665c255d 2023-08-04 jrmu (test-eval '(f 16) true)
1066 665c255d 2023-08-04 jrmu (test-eval
1067 665c255d 2023-08-04 jrmu '(letrec ((fact
1068 665c255d 2023-08-04 jrmu (lambda (n)
1069 665c255d 2023-08-04 jrmu (if (= n 1)
1071 665c255d 2023-08-04 jrmu (* n (fact (- n 1)))))))
1072 665c255d 2023-08-04 jrmu (fact 10))
1076 665c255d 2023-08-04 jrmu (test-eval '(amb 1 2 3) 1)
1077 665c255d 2023-08-04 jrmu (test-eval 'try-again 2)
1078 665c255d 2023-08-04 jrmu (test-eval 'try-again 3)
1079 665c255d 2023-08-04 jrmu (test-eval 'try-again "No alternatives")
1080 665c255d 2023-08-04 jrmu (test-eval 'try-again "No current problem")
1081 665c255d 2023-08-04 jrmu (test-eval 'try-again "No current problem")
1082 665c255d 2023-08-04 jrmu (test-eval '(amb (amb 1 2) (amb 'a 'b))
1084 665c255d 2023-08-04 jrmu (test-eval 'try-again 2)
1085 665c255d 2023-08-04 jrmu (test-eval 'try-again 'a)
1086 665c255d 2023-08-04 jrmu (test-eval 'try-again 'b)
1087 665c255d 2023-08-04 jrmu (test-eval 'try-again "No alternatives")
1088 665c255d 2023-08-04 jrmu (geval '(define (require p) (if (not p) (amb))))
1089 665c255d 2023-08-04 jrmu (test-eval '(require false) "No alternatives")
1090 665c255d 2023-08-04 jrmu (test-eval '(require true) false)
1094 665c255d 2023-08-04 jrmu '(define (an-integer-between low high)
1095 665c255d 2023-08-04 jrmu (require (<= low high))
1096 665c255d 2023-08-04 jrmu (amb low (an-integer-between (+ low 1) high))))
1099 665c255d 2023-08-04 jrmu '(define (a-pythagorean-triple-between low high)
1100 665c255d 2023-08-04 jrmu (let ((i (an-integer-between low high)))
1101 665c255d 2023-08-04 jrmu (let ((j (an-integer-between i high)))
1102 665c255d 2023-08-04 jrmu (let ((k (an-integer-between j high)))
1103 665c255d 2023-08-04 jrmu (require (= (+ (* i i) (* j j)) (* k k)))
1104 665c255d 2023-08-04 jrmu (list i j k))))))
1106 665c255d 2023-08-04 jrmu ;; (test-eval
1107 665c255d 2023-08-04 jrmu ;; '(a-pythagorean-triple-between 1 20)
1108 665c255d 2023-08-04 jrmu ;; '(3 4 5))
1109 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(5 12 13))
1110 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(6 8 10))
1111 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(8 15 17))
1112 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(9 12 15))
1115 665c255d 2023-08-04 jrmu '(define (an-integer-starting-from low)
1116 665c255d 2023-08-04 jrmu (amb low (an-integer-starting-from (+ low 1)))))
1119 665c255d 2023-08-04 jrmu '(define (pythagorean-triples-starting-from low)
1120 665c255d 2023-08-04 jrmu (let* ((k (an-integer-starting-from low))
1121 665c255d 2023-08-04 jrmu (i (an-integer-between low k))
1122 665c255d 2023-08-04 jrmu (j (an-integer-between i k)))
1123 665c255d 2023-08-04 jrmu (require (= (+ (* i i) (* j j)) (* k k)))
1124 665c255d 2023-08-04 jrmu (list i j k))))
1126 665c255d 2023-08-04 jrmu ;; (test-eval '(pythagorean-triples-starting-from 1)
1127 665c255d 2023-08-04 jrmu ;; '(3 4 5))
1128 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(6 8 10))
1129 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(5 12 13))
1130 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(9 12 15))
1131 665c255d 2023-08-04 jrmu ;; (test-eval 'try-again '(8 15 17))
1134 665c255d 2023-08-04 jrmu '(define (next-triplet trp)
1135 665c255d 2023-08-04 jrmu (let ((i (car trp))
1136 665c255d 2023-08-04 jrmu (j (cadr trp))
1137 665c255d 2023-08-04 jrmu (k (caddr trp)))
1138 665c255d 2023-08-04 jrmu (cond ((= i j k) (list 1 1 (+ k 1)))
1139 665c255d 2023-08-04 jrmu ((= j k) (list (+ i 1) (+ i 1) k))
1140 665c255d 2023-08-04 jrmu (else (list i (+ j 1) k))))))
1142 665c255d 2023-08-04 jrmu '(define (triplet-starting-from trp)
1143 665c255d 2023-08-04 jrmu (amb trp (triplet-starting-from (next-triplet trp)))))
1145 665c255d 2023-08-04 jrmu '(define (pythagorean-triples-starting-from low)
1146 665c255d 2023-08-04 jrmu (let* ((triplet (triplet-starting-from (list low low low)))
1147 665c255d 2023-08-04 jrmu (i (car triplet))
1148 665c255d 2023-08-04 jrmu (j (cadr triplet))
1149 665c255d 2023-08-04 jrmu (k (caddr triplet)))
1150 665c255d 2023-08-04 jrmu (require (= (+ (* i i) (* j j)) (* k k)))
1151 665c255d 2023-08-04 jrmu (list i j k))))
1153 665c255d 2023-08-04 jrmu '(define (distinct? items)
1154 665c255d 2023-08-04 jrmu (cond ((null? items) true)
1155 665c255d 2023-08-04 jrmu ((null? (cdr items)) true)
1156 665c255d 2023-08-04 jrmu ((member (car items) (cdr items)) false)
1157 665c255d 2023-08-04 jrmu (else (distinct? (cdr items))))))
1160 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.
1162 665c255d 2023-08-04 jrmu ;; (define (queens queen-positions n)
1163 665c255d 2023-08-04 jrmu ;; (if (= (length queen-positions) n)
1164 665c255d 2023-08-04 jrmu ;; queen-positions
1165 665c255d 2023-08-04 jrmu ;; (let ((new-position (amb 1 2 3 4 5 6 7 8)))
1166 665c255d 2023-08-04 jrmu ;; (adjoin new-position queen-positions)
1167 665c255d 2023-08-04 jrmu ;; (require (safe? queen-positions))
1168 665c255d 2023-08-04 jrmu ;; (queens queen-positions n)
1171 665c255d 2023-08-04 jrmu '(define (queens board-size)
1172 665c255d 2023-08-04 jrmu (define (queen-cols k)
1173 665c255d 2023-08-04 jrmu (if (= k 0)
1174 665c255d 2023-08-04 jrmu empty-board
1175 665c255d 2023-08-04 jrmu (let* ((new-position (an-integer-between 1 board-size))
1176 665c255d 2023-08-04 jrmu (new-positions
1177 665c255d 2023-08-04 jrmu (adjoin-position new-position k (queen-cols (- k 1)))))
1178 665c255d 2023-08-04 jrmu (require (safe? k new-positions))
1179 665c255d 2023-08-04 jrmu new-positions)))
1180 665c255d 2023-08-04 jrmu (queen-cols board-size)))
1182 665c255d 2023-08-04 jrmu ;; For example, '((2 4 1 3)) might represent a solution to the 4-queens problem. This represents having queens in col#1 row#2, col#2 row#4, col#3 row#1, col#4 row#3.
1184 665c255d 2023-08-04 jrmu '(define empty-board '()))
1186 665c255d 2023-08-04 jrmu ;; take positions and append new-queen-row in the (new-queen-col - 1)st position in the list
1188 665c255d 2023-08-04 jrmu '(define (adjoin-position new-queen-row new-queen-col positions)
1189 665c255d 2023-08-04 jrmu (append positions
1190 665c255d 2023-08-04 jrmu (list new-queen-row))))
1193 665c255d 2023-08-04 jrmu '(define (safe? col positions)
1194 665c255d 2023-08-04 jrmu (define (exclude-last lst)
1195 665c255d 2023-08-04 jrmu (cond ((null? lst) (error "empty list"))
1196 665c255d 2023-08-04 jrmu ((null? (cdr lst)) '())
1197 665c255d 2023-08-04 jrmu (else (cons (car lst) (exclude-last (cdr lst))))))
1198 665c255d 2023-08-04 jrmu (let ((row (list-ref positions (- col 1)))
1199 665c255d 2023-08-04 jrmu (all-but-last (exclude-last positions)))
1200 665c255d 2023-08-04 jrmu (let ((same-row?
1201 665c255d 2023-08-04 jrmu (fold-left (lambda (result next-row)
1202 665c255d 2023-08-04 jrmu (or result
1203 665c255d 2023-08-04 jrmu (= next-row row)))
1205 665c255d 2023-08-04 jrmu all-but-last))
1206 665c255d 2023-08-04 jrmu (same-positive-diagonal?
1207 665c255d 2023-08-04 jrmu (fold-left (lambda (result row-col-sum)
1208 665c255d 2023-08-04 jrmu (or result
1209 665c255d 2023-08-04 jrmu (= (+ row col) row-col-sum)))
1211 665c255d 2023-08-04 jrmu (map-2 + all-but-last (enumerate-interval 1 (- col 1)))))
1212 665c255d 2023-08-04 jrmu (same-negative-diagonal?
1213 665c255d 2023-08-04 jrmu (fold-left (lambda (result row-col-dif)
1214 665c255d 2023-08-04 jrmu (or result
1215 665c255d 2023-08-04 jrmu (= (- row col) row-col-dif)))
1217 665c255d 2023-08-04 jrmu (map-2 - all-but-last (enumerate-interval 1 (- col 1))))))
1218 665c255d 2023-08-04 jrmu (not (or same-row? same-positive-diagonal? same-negative-diagonal?))))))
1220 665c255d 2023-08-04 jrmu (test-eval '(safe? 1 '(1)) #t)
1221 665c255d 2023-08-04 jrmu (test-eval '(safe? 4 '(2 4 1 1)) #f)
1222 665c255d 2023-08-04 jrmu (test-eval '(safe? 4 '(2 4 1 2)) #f)
1223 665c255d 2023-08-04 jrmu (test-eval '(safe? 4 '(2 4 1 3)) #t)
1224 665c255d 2023-08-04 jrmu (test-eval '(safe? 4 '(2 4 1 4)) #f)
1225 665c255d 2023-08-04 jrmu (test-eval '(safe? 7 '(2 4 6 8 3 1 1)) #f)
1226 665c255d 2023-08-04 jrmu (test-eval '(safe? 7 '(2 4 6 8 3 1 2)) #f)
1227 665c255d 2023-08-04 jrmu (test-eval '(safe? 7 '(2 4 6 8 3 1 3)) #f)
1228 665c255d 2023-08-04 jrmu (test-eval '(safe? 7 '(2 4 6 8 3 1 4)) #f)
1229 665c255d 2023-08-04 jrmu (test-eval '(safe? 7 '(2 4 6 8 3 1 5)) #f)
1230 665c255d 2023-08-04 jrmu (test-eval '(safe? 7 '(2 4 6 8 3 1 6)) #f)
1231 665c255d 2023-08-04 jrmu (test-eval '(safe? 7 '(2 4 6 8 3 1 7)) #t)
1232 665c255d 2023-08-04 jrmu (test-eval '(safe? 7 '(2 4 6 8 3 1 8)) #f)
1235 665c255d 2023-08-04 jrmu (user-print (geval '(queens 4)))
1236 665c255d 2023-08-04 jrmu (user-print (geval 'try-again))
1237 665c255d 2023-08-04 jrmu (user-print (geval 'try-again))
1238 665c255d 2023-08-04 jrmu (user-print (geval '(queens 5)))
1239 665c255d 2023-08-04 jrmu (user-print (geval 'try-again))
1240 665c255d 2023-08-04 jrmu (user-print (geval 'try-again))
1241 665c255d 2023-08-04 jrmu (user-print (geval 'try-again))
1243 665c255d 2023-08-04 jrmu ;; the procedure is really slow but it works
