1 665c255d 2023-08-04 jrmu ;; (define apply-in-underlying-scheme apply)
3 665c255d 2023-08-04 jrmu (define (eval exp env)
4 665c255d 2023-08-04 jrmu (cond ((self-evaluating? exp) exp)
5 665c255d 2023-08-04 jrmu ((variable? exp) (lookup-variable-value exp env))
6 665c255d 2023-08-04 jrmu ((quoted? exp) (text-of-quotation exp))
7 665c255d 2023-08-04 jrmu ((assignment? exp) (eval-assignment exp env))
8 665c255d 2023-08-04 jrmu ((definition? exp) (eval-definition exp env))
9 665c255d 2023-08-04 jrmu ;; ((unbound? exp) (eval-unbound exp env))
10 665c255d 2023-08-04 jrmu ((if? exp) (eval-if exp env))
11 665c255d 2023-08-04 jrmu ((and? exp) (eval-and exp env))
12 665c255d 2023-08-04 jrmu ((or? exp) (eval-or exp env))
13 665c255d 2023-08-04 jrmu ((lambda? exp)
14 665c255d 2023-08-04 jrmu (make-procedure (lambda-parameters exp)
15 665c255d 2023-08-04 jrmu (lambda-body exp)
17 665c255d 2023-08-04 jrmu ((begin? exp)
18 665c255d 2023-08-04 jrmu (eval-sequence (begin-actions exp) env))
19 665c255d 2023-08-04 jrmu ((cond? exp) (eval (cond->if exp) env))
20 665c255d 2023-08-04 jrmu ((let? exp) (eval (let->combination exp) env))
21 665c255d 2023-08-04 jrmu ((let*? exp) (eval (let*->nested-lets exp) env))
22 665c255d 2023-08-04 jrmu ((named-let? exp) (eval (named-let->combination exp) env))
23 665c255d 2023-08-04 jrmu ((do? exp) (eval (do->combination exp) env))
24 665c255d 2023-08-04 jrmu ((application? exp)
25 665c255d 2023-08-04 jrmu (apply (eval (operator exp) env)
26 665c255d 2023-08-04 jrmu (list-of-values (operands exp) env)))
28 665c255d 2023-08-04 jrmu (error "Unknown expression type -- EVAL" exp))))
29 665c255d 2023-08-04 jrmu (define (apply procedure arguments)
30 665c255d 2023-08-04 jrmu (cond ((primitive-procedure? procedure)
31 665c255d 2023-08-04 jrmu (apply-primitive-procedure procedure arguments))
32 665c255d 2023-08-04 jrmu ((compound-procedure? procedure)
33 665c255d 2023-08-04 jrmu (eval-sequence
34 665c255d 2023-08-04 jrmu (procedure-body procedure)
35 665c255d 2023-08-04 jrmu (extend-environment
36 665c255d 2023-08-04 jrmu (procedure-parameters procedure)
38 665c255d 2023-08-04 jrmu (procedure-environment procedure))))
41 665c255d 2023-08-04 jrmu "Unknown procedure type -- APPLY" procedure))))
43 665c255d 2023-08-04 jrmu (define (list-of-values exps env)
44 665c255d 2023-08-04 jrmu (if (no-operands? exps)
46 665c255d 2023-08-04 jrmu (cons (eval (first-operand exps) env)
47 665c255d 2023-08-04 jrmu (list-of-values (rest-operands exps) env))))
49 665c255d 2023-08-04 jrmu (define (tagged-list? exp tag)
50 665c255d 2023-08-04 jrmu (if (pair? exp)
51 665c255d 2023-08-04 jrmu (eq? (car exp) tag)
54 665c255d 2023-08-04 jrmu ;; self-evaluating/variable/quoted
55 665c255d 2023-08-04 jrmu (define (self-evaluating? exp)
56 665c255d 2023-08-04 jrmu (cond ((number? exp) true)
57 665c255d 2023-08-04 jrmu ((string? exp) true)
58 665c255d 2023-08-04 jrmu (else false)))
59 665c255d 2023-08-04 jrmu (define (variable? exp) (symbol? exp))
60 665c255d 2023-08-04 jrmu (define (quoted? exp)
61 665c255d 2023-08-04 jrmu (tagged-list? exp 'quote))
62 665c255d 2023-08-04 jrmu (define (text-of-quotation exp) (cadr exp))
64 665c255d 2023-08-04 jrmu ;; assignment/definition
65 665c255d 2023-08-04 jrmu (define (assignment? exp)
66 665c255d 2023-08-04 jrmu (tagged-list? exp 'set!))
67 665c255d 2023-08-04 jrmu (define (assignment-variable exp) (cadr exp))
68 665c255d 2023-08-04 jrmu (define (assignment-value exp) (caddr exp))
69 665c255d 2023-08-04 jrmu (define (make-assignment var val)
70 665c255d 2023-08-04 jrmu (list 'set! var val))
71 665c255d 2023-08-04 jrmu (define (definition? exp)
72 665c255d 2023-08-04 jrmu (tagged-list? exp 'define))
73 665c255d 2023-08-04 jrmu (define (definition-variable exp)
74 665c255d 2023-08-04 jrmu (if (symbol? (cadr exp))
76 665c255d 2023-08-04 jrmu (caadr exp)))
77 665c255d 2023-08-04 jrmu (define (definition-value exp)
78 665c255d 2023-08-04 jrmu (if (symbol? (cadr exp))
80 665c255d 2023-08-04 jrmu (make-lambda (cdadr exp) ; formal parameters
81 665c255d 2023-08-04 jrmu (cddr exp)))) ; body
82 665c255d 2023-08-04 jrmu (define (eval-assignment exp env)
83 665c255d 2023-08-04 jrmu (set-variable-value! (assignment-variable exp)
84 665c255d 2023-08-04 jrmu (eval (assignment-value exp) env)
87 665c255d 2023-08-04 jrmu (define (eval-definition exp env)
88 665c255d 2023-08-04 jrmu (define-variable! (definition-variable exp)
89 665c255d 2023-08-04 jrmu (eval (definition-value exp) env)
92 665c255d 2023-08-04 jrmu (define (make-definition var val)
93 665c255d 2023-08-04 jrmu `(define ,var ,val))
95 665c255d 2023-08-04 jrmu ;; make-unbound!
97 665c255d 2023-08-04 jrmu ;; (define (unbound? exp)
98 665c255d 2023-08-04 jrmu ;; (tagged-list? exp 'make-unbound!))
99 665c255d 2023-08-04 jrmu ;; (define (unbound-var exp)
100 665c255d 2023-08-04 jrmu ;; (cadr exp))
101 665c255d 2023-08-04 jrmu ;; (define (eval-unbound exp env)
102 665c255d 2023-08-04 jrmu ;; (remove-binding-from-frame! (unbound-var exp) (first-frame env)))
106 665c255d 2023-08-04 jrmu ;; if/and/or
107 665c255d 2023-08-04 jrmu (define (if? exp) (tagged-list? exp 'if))
108 665c255d 2023-08-04 jrmu (define (if-predicate exp) (cadr exp))
109 665c255d 2023-08-04 jrmu (define (if-consequent exp) (caddr exp))
110 665c255d 2023-08-04 jrmu (define (if-alternative exp)
111 665c255d 2023-08-04 jrmu (if (not (null? (cdddr exp)))
112 665c255d 2023-08-04 jrmu (cadddr exp)
114 665c255d 2023-08-04 jrmu (define (make-if predicate consequent alternative)
115 665c255d 2023-08-04 jrmu (list 'if predicate consequent alternative))
116 665c255d 2023-08-04 jrmu (define (eval-if exp env)
117 665c255d 2023-08-04 jrmu (if (true? (eval (if-predicate exp) env))
118 665c255d 2023-08-04 jrmu (eval (if-consequent exp) env)
119 665c255d 2023-08-04 jrmu (eval (if-alternative exp) env)))
121 665c255d 2023-08-04 jrmu (define (and? exp)
122 665c255d 2023-08-04 jrmu (tagged-list? exp 'and))
123 665c255d 2023-08-04 jrmu (define (and-clauses exp)
125 665c255d 2023-08-04 jrmu (define (or? exp)
126 665c255d 2023-08-04 jrmu (tagged-list? exp 'or))
127 665c255d 2023-08-04 jrmu (define (or-clauses exp)
129 665c255d 2023-08-04 jrmu (define (eval-and exp env)
130 665c255d 2023-08-04 jrmu (define (eval-clauses clauses)
131 665c255d 2023-08-04 jrmu (cond ((null? clauses) true)
132 665c255d 2023-08-04 jrmu ((null? (cdr clauses)) (eval (car clauses) env))
133 665c255d 2023-08-04 jrmu (else (and (eval (car clauses) env)
134 665c255d 2023-08-04 jrmu (eval-clauses (cdr clauses))))))
135 665c255d 2023-08-04 jrmu (eval-clauses (and-clauses exp)))
136 665c255d 2023-08-04 jrmu (define (eval-or exp env)
137 665c255d 2023-08-04 jrmu (define (eval-clauses clauses)
138 665c255d 2023-08-04 jrmu (if (null? clauses)
140 665c255d 2023-08-04 jrmu (or (eval (car clauses) env)
141 665c255d 2023-08-04 jrmu (eval-clauses (cdr clauses)))))
142 665c255d 2023-08-04 jrmu (eval-clauses (or-clauses exp)))
145 665c255d 2023-08-04 jrmu ;; lambda/let/let*
146 665c255d 2023-08-04 jrmu (define (lambda? exp) (tagged-list? exp 'lambda))
147 665c255d 2023-08-04 jrmu (define (lambda-parameters exp) (cadr exp))
148 665c255d 2023-08-04 jrmu (define (lambda-body exp) (cddr exp))
149 665c255d 2023-08-04 jrmu (define (make-lambda parameters body)
150 665c255d 2023-08-04 jrmu (cons 'lambda (cons parameters body)))
152 665c255d 2023-08-04 jrmu (define (make-let vars vals body)
154 665c255d 2023-08-04 jrmu (cons (map list vars vals)
156 665c255d 2023-08-04 jrmu (define (let? exp)
157 665c255d 2023-08-04 jrmu (and (tagged-list? exp 'let)
158 665c255d 2023-08-04 jrmu (not (symbol? (cadr exp)))))
159 665c255d 2023-08-04 jrmu (define (let-vars exp)
160 665c255d 2023-08-04 jrmu (map car (cadr exp)))
161 665c255d 2023-08-04 jrmu (define (let-vals exp)
162 665c255d 2023-08-04 jrmu (map cadr (cadr exp)))
163 665c255d 2023-08-04 jrmu (define (let-body exp)
164 665c255d 2023-08-04 jrmu (cddr exp))
165 665c255d 2023-08-04 jrmu (define (let->combination exp)
166 665c255d 2023-08-04 jrmu (make-application (make-lambda (let-vars exp) (let-body exp))
167 665c255d 2023-08-04 jrmu (let-vals exp)))
168 665c255d 2023-08-04 jrmu (define (named-let? exp)
169 665c255d 2023-08-04 jrmu (and (tagged-list? exp 'let)
170 665c255d 2023-08-04 jrmu (symbol? (cadr exp))))
171 665c255d 2023-08-04 jrmu (define (named-let-name exp)
172 665c255d 2023-08-04 jrmu (cadr exp))
173 665c255d 2023-08-04 jrmu (define (named-let-vars exp)
174 665c255d 2023-08-04 jrmu (map car (caddr exp)))
175 665c255d 2023-08-04 jrmu (define (named-let-vals exp)
176 665c255d 2023-08-04 jrmu (map cadr (caddr exp)))
177 665c255d 2023-08-04 jrmu (define (named-let-body exp)
178 665c255d 2023-08-04 jrmu (cdddr exp))
179 665c255d 2023-08-04 jrmu (define (named-let->combination exp)
180 665c255d 2023-08-04 jrmu (sequence->exp
181 665c255d 2023-08-04 jrmu (list (make-definition (named-let-name exp)
182 665c255d 2023-08-04 jrmu (make-lambda (named-let-vars exp)
183 665c255d 2023-08-04 jrmu (named-let-body exp)))
184 665c255d 2023-08-04 jrmu (make-application (named-let-name exp)
185 665c255d 2023-08-04 jrmu (named-let-vals exp)))))
186 665c255d 2023-08-04 jrmu (define (make-named-let name vars vals body)
189 665c255d 2023-08-04 jrmu (cons (map list vars vals)
192 665c255d 2023-08-04 jrmu (define (make-application op args)
193 665c255d 2023-08-04 jrmu (cons op args))
195 665c255d 2023-08-04 jrmu (define (let*? exp)
196 665c255d 2023-08-04 jrmu (tagged-list? exp 'let*))
197 665c255d 2023-08-04 jrmu (define let*-vars let-vars)
198 665c255d 2023-08-04 jrmu (define let*-vals let-vals)
199 665c255d 2023-08-04 jrmu (define let*-body let-body)
200 665c255d 2023-08-04 jrmu (define (let*->nested-lets exp)
201 665c255d 2023-08-04 jrmu (define (expand-lets vars vals)
202 665c255d 2023-08-04 jrmu (if (null? (cdr vars))
203 665c255d 2023-08-04 jrmu (make-let (list (car vars))
204 665c255d 2023-08-04 jrmu (list (car vals))
205 665c255d 2023-08-04 jrmu (let*-body exp))
206 665c255d 2023-08-04 jrmu (make-let (list (car vars))
207 665c255d 2023-08-04 jrmu (list (car vals))
208 665c255d 2023-08-04 jrmu (list (expand-lets (cdr vars) (cdr vals))))))
209 665c255d 2023-08-04 jrmu (let ((vars (let*-vars exp))
210 665c255d 2023-08-04 jrmu (vals (let*-vals exp)))
211 665c255d 2023-08-04 jrmu (if (null? vars)
212 665c255d 2023-08-04 jrmu (sequence->exp (let*-body exp))
213 665c255d 2023-08-04 jrmu (expand-lets vars vals))))
216 665c255d 2023-08-04 jrmu (define (do? exp)
217 665c255d 2023-08-04 jrmu (tagged-list? exp 'do))
218 665c255d 2023-08-04 jrmu (define (do-vars exp)
219 665c255d 2023-08-04 jrmu (map car (cadr exp)))
220 665c255d 2023-08-04 jrmu (define (do-inits exp)
221 665c255d 2023-08-04 jrmu (map cadr (cadr exp)))
222 665c255d 2023-08-04 jrmu (define (do-steps exp)
223 665c255d 2023-08-04 jrmu (map (lambda (var-init-step)
224 665c255d 2023-08-04 jrmu (if (null? (cddr var-init-step))
225 665c255d 2023-08-04 jrmu (car var-init-step)
226 665c255d 2023-08-04 jrmu (caddr var-init-step)))
227 665c255d 2023-08-04 jrmu (cadr exp)))
228 665c255d 2023-08-04 jrmu (define (do-test exp)
229 665c255d 2023-08-04 jrmu (caaddr exp))
230 665c255d 2023-08-04 jrmu (define (do-expressions exp)
231 665c255d 2023-08-04 jrmu (if (null? (cdaddr exp))
232 665c255d 2023-08-04 jrmu (caddr exp)
233 665c255d 2023-08-04 jrmu (cdaddr exp)))
234 665c255d 2023-08-04 jrmu (define (do-commands exp)
235 665c255d 2023-08-04 jrmu (cdddr exp))
236 665c255d 2023-08-04 jrmu (define (do->combination exp)
237 665c255d 2023-08-04 jrmu (make-named-let
239 665c255d 2023-08-04 jrmu (do-vars exp)
240 665c255d 2023-08-04 jrmu (do-inits exp)
243 665c255d 2023-08-04 jrmu (do-test exp)
244 665c255d 2023-08-04 jrmu (sequence->exp (do-expressions exp))
245 665c255d 2023-08-04 jrmu (sequence->exp
246 665c255d 2023-08-04 jrmu (append (do-commands exp)
247 665c255d 2023-08-04 jrmu (list (make-application
249 665c255d 2023-08-04 jrmu (do-steps exp)))))))))
252 665c255d 2023-08-04 jrmu ;; begin/sequence
253 665c255d 2023-08-04 jrmu (define (begin? exp) (tagged-list? exp 'begin))
254 665c255d 2023-08-04 jrmu (define (begin-actions exp) (cdr exp))
255 665c255d 2023-08-04 jrmu (define (last-exp? seq) (null? (cdr seq)))
256 665c255d 2023-08-04 jrmu (define (first-exp seq) (car seq))
257 665c255d 2023-08-04 jrmu (define (rest-exps seq) (cdr seq))
258 665c255d 2023-08-04 jrmu (define (sequence->exp seq)
259 665c255d 2023-08-04 jrmu (cond ((null? seq) seq)
260 665c255d 2023-08-04 jrmu ((last-exp? seq) (first-exp seq))
261 665c255d 2023-08-04 jrmu (else (make-begin seq))))
262 665c255d 2023-08-04 jrmu (define (make-begin seq) (cons 'begin seq))
263 665c255d 2023-08-04 jrmu (define (eval-sequence exps env)
264 665c255d 2023-08-04 jrmu (cond ((last-exp? exps) (eval (first-exp exps) env))
265 665c255d 2023-08-04 jrmu (else (eval (first-exp exps) env)
266 665c255d 2023-08-04 jrmu (eval-sequence (rest-exps exps) env))))
268 665c255d 2023-08-04 jrmu ;; application
269 665c255d 2023-08-04 jrmu (define (application? exp) (pair? exp))
270 665c255d 2023-08-04 jrmu (define (operator exp) (car exp))
271 665c255d 2023-08-04 jrmu (define (operands exp) (cdr exp))
272 665c255d 2023-08-04 jrmu (define (no-operands? ops) (null? ops))
273 665c255d 2023-08-04 jrmu (define (first-operand ops) (car ops))
274 665c255d 2023-08-04 jrmu (define (rest-operands ops) (cdr ops))
277 665c255d 2023-08-04 jrmu (define (cond? exp) (tagged-list? exp 'cond))
278 665c255d 2023-08-04 jrmu (define (cond-clauses exp) (cdr exp))
279 665c255d 2023-08-04 jrmu (define (cond-else-clause? clause)
280 665c255d 2023-08-04 jrmu (eq? (cond-predicate clause) 'else))
281 665c255d 2023-08-04 jrmu (define (cond-predicate clause) (car clause))
282 665c255d 2023-08-04 jrmu (define (cond-actions clause) (cdr clause))
283 665c255d 2023-08-04 jrmu (define (cond-extended-clause? clause)
284 665c255d 2023-08-04 jrmu (and (not (null? (cdr clause))) (eq? (cadr clause) '=>)))
285 665c255d 2023-08-04 jrmu (define (cond-extended-proc clause)
286 665c255d 2023-08-04 jrmu (caddr clause))
287 665c255d 2023-08-04 jrmu (define (cond->if exp)
288 665c255d 2023-08-04 jrmu (expand-clauses (cond-clauses exp)))
289 665c255d 2023-08-04 jrmu (define (expand-clauses clauses)
290 665c255d 2023-08-04 jrmu (if (null? clauses)
291 665c255d 2023-08-04 jrmu 'false ; no else clause
292 665c255d 2023-08-04 jrmu (let ((first (car clauses))
293 665c255d 2023-08-04 jrmu (rest (cdr clauses)))
294 665c255d 2023-08-04 jrmu (if (cond-else-clause? first)
295 665c255d 2023-08-04 jrmu (if (null? rest)
296 665c255d 2023-08-04 jrmu (sequence->exp (cond-actions first))
297 665c255d 2023-08-04 jrmu (error "ELSE clause isn't last -- COND->IF"
299 665c255d 2023-08-04 jrmu (if (cond-extended-clause? first)
300 665c255d 2023-08-04 jrmu (make-if (cond-predicate first)
301 665c255d 2023-08-04 jrmu (make-application
302 665c255d 2023-08-04 jrmu (cond-extended-proc first)
303 665c255d 2023-08-04 jrmu (list (cond-predicate first)))
304 665c255d 2023-08-04 jrmu (expand-clauses rest))
305 665c255d 2023-08-04 jrmu (make-if (cond-predicate first)
306 665c255d 2023-08-04 jrmu (sequence->exp (cond-actions first))
307 665c255d 2023-08-04 jrmu (expand-clauses rest)))))))
308 665c255d 2023-08-04 jrmu (define (true? x)
309 665c255d 2023-08-04 jrmu (not (eq? x false)))
310 665c255d 2023-08-04 jrmu (define (false? x)
311 665c255d 2023-08-04 jrmu (eq? x false))
313 665c255d 2023-08-04 jrmu ;; procedure
314 665c255d 2023-08-04 jrmu (define (make-procedure parameters body env)
315 665c255d 2023-08-04 jrmu (list 'procedure parameters (scan-out-defines body) env))
316 665c255d 2023-08-04 jrmu (define (scan-out-defines body)
317 665c255d 2023-08-04 jrmu (let* ((definitions (filter definition? body))
318 665c255d 2023-08-04 jrmu (vars (map definition-variable definitions))
319 665c255d 2023-08-04 jrmu (unassigneds (map (lambda (var) ''*unassigned*)
321 665c255d 2023-08-04 jrmu (vals (map definition-value definitions))
322 665c255d 2023-08-04 jrmu (assignments
323 665c255d 2023-08-04 jrmu (map (lambda (var val)
324 665c255d 2023-08-04 jrmu (make-assignment var val))
325 665c255d 2023-08-04 jrmu vars vals))
326 665c255d 2023-08-04 jrmu (exps (remove definition? body)))
327 665c255d 2023-08-04 jrmu (if (null? definitions)
330 665c255d 2023-08-04 jrmu (make-let vars
331 665c255d 2023-08-04 jrmu unassigneds
332 665c255d 2023-08-04 jrmu (append assignments exps))))))
333 665c255d 2023-08-04 jrmu (define (compound-procedure? p)
334 665c255d 2023-08-04 jrmu (tagged-list? p 'procedure))
335 665c255d 2023-08-04 jrmu (define (procedure-parameters p) (cadr p))
336 665c255d 2023-08-04 jrmu (define (procedure-body p) (caddr p))
337 665c255d 2023-08-04 jrmu (define (procedure-environment p) (cadddr p))
339 665c255d 2023-08-04 jrmu ;; environment
340 665c255d 2023-08-04 jrmu (define (enclosing-environment env) (cdr env))
341 665c255d 2023-08-04 jrmu (define (first-frame env) (car env))
342 665c255d 2023-08-04 jrmu (define the-empty-environment '())
343 665c255d 2023-08-04 jrmu (define (make-frame variables values)
344 665c255d 2023-08-04 jrmu (cons variables values))
345 665c255d 2023-08-04 jrmu (define (frame-variables frame) (car frame))
346 665c255d 2023-08-04 jrmu (define (frame-values frame) (cdr frame))
347 665c255d 2023-08-04 jrmu (define (add-binding-to-frame! var val frame)
348 665c255d 2023-08-04 jrmu (set-car! frame (cons var (car frame)))
349 665c255d 2023-08-04 jrmu (set-cdr! frame (cons val (cdr frame))))
350 665c255d 2023-08-04 jrmu (define (extend-environment vars vals base-env)
351 665c255d 2023-08-04 jrmu (if (= (length vars) (length vals))
352 665c255d 2023-08-04 jrmu (cons (make-frame vars vals) base-env)
353 665c255d 2023-08-04 jrmu (if (< (length vars) (length vals))
354 665c255d 2023-08-04 jrmu (error "Too many arguments supplied" vars vals)
355 665c255d 2023-08-04 jrmu (error "Too few arguments supplied" vars vals))))
356 665c255d 2023-08-04 jrmu (define (lookup-variable-value var env)
357 665c255d 2023-08-04 jrmu (define (env-loop env)
358 665c255d 2023-08-04 jrmu (define (scan vars vals)
359 665c255d 2023-08-04 jrmu (cond ((null? vars)
360 665c255d 2023-08-04 jrmu (env-loop (enclosing-environment env)))
361 665c255d 2023-08-04 jrmu ((eq? var (car vars))
362 665c255d 2023-08-04 jrmu (let ((val (car vals)))
363 665c255d 2023-08-04 jrmu (if (eq? val '*unassigned*)
364 665c255d 2023-08-04 jrmu (error "Var not yet defined -- LOOKUP-VARIABLE-VALUE" var)
366 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
367 665c255d 2023-08-04 jrmu (if (eq? env the-empty-environment)
368 665c255d 2023-08-04 jrmu (error "Unbound variable" var)
369 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
370 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
371 665c255d 2023-08-04 jrmu (frame-values frame)))))
372 665c255d 2023-08-04 jrmu (env-loop env))
373 665c255d 2023-08-04 jrmu (define (set-variable-value! var val env)
374 665c255d 2023-08-04 jrmu (define (env-loop env)
375 665c255d 2023-08-04 jrmu (define (scan vars vals)
376 665c255d 2023-08-04 jrmu (cond ((null? vars)
377 665c255d 2023-08-04 jrmu (env-loop (enclosing-environment env)))
378 665c255d 2023-08-04 jrmu ((eq? var (car vars))
379 665c255d 2023-08-04 jrmu (set-car! vals val))
380 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
381 665c255d 2023-08-04 jrmu (if (eq? env the-empty-environment)
382 665c255d 2023-08-04 jrmu (error "Unbound variable -- SET!" var)
383 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
384 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
385 665c255d 2023-08-04 jrmu (frame-values frame)))))
386 665c255d 2023-08-04 jrmu (env-loop env))
387 665c255d 2023-08-04 jrmu (define (define-variable! var val env)
388 665c255d 2023-08-04 jrmu (let ((frame (first-frame env)))
389 665c255d 2023-08-04 jrmu (define (scan vars vals)
390 665c255d 2023-08-04 jrmu (cond ((null? vars)
391 665c255d 2023-08-04 jrmu (add-binding-to-frame! var val frame))
392 665c255d 2023-08-04 jrmu ((eq? var (car vars))
393 665c255d 2023-08-04 jrmu (set-car! vals val))
394 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
395 665c255d 2023-08-04 jrmu (scan (frame-variables frame)
396 665c255d 2023-08-04 jrmu (frame-values frame))))
398 665c255d 2023-08-04 jrmu (define (remove-binding-from-frame! var frame)
399 665c255d 2023-08-04 jrmu (define (scan vars vals)
400 665c255d 2023-08-04 jrmu (cond ((null? (cdr vars))
401 665c255d 2023-08-04 jrmu (error "Binding not found -- REMOVE-BINDING-FROM-FRAME!" var))
402 665c255d 2023-08-04 jrmu ((eq? var (cadr vars))
403 665c255d 2023-08-04 jrmu (set-cdr! vars (cddr vars))
404 665c255d 2023-08-04 jrmu (set-cdr! vals (cddr vals)))
405 665c255d 2023-08-04 jrmu (else (scan (cdr vars) (cdr vals)))))
406 665c255d 2023-08-04 jrmu (let ((vars (frame-variables frame))
407 665c255d 2023-08-04 jrmu (vals (frame-values frame)))
408 665c255d 2023-08-04 jrmu (if (eq? var (car vars))
409 665c255d 2023-08-04 jrmu (begin (set-car! frame (cdr vars))
410 665c255d 2023-08-04 jrmu (set-cdr! frame (cdr vals)))
411 665c255d 2023-08-04 jrmu (scan vars vals))))
413 665c255d 2023-08-04 jrmu ;; primitives
414 665c255d 2023-08-04 jrmu (define (primitive-procedure? proc)
415 665c255d 2023-08-04 jrmu (tagged-list? proc 'primitive))
416 665c255d 2023-08-04 jrmu (define (primitive-implementation proc) (cadr proc))
417 665c255d 2023-08-04 jrmu (define primitive-procedures
418 665c255d 2023-08-04 jrmu (list (list 'car car)
419 665c255d 2023-08-04 jrmu (list 'cdr cdr)
420 665c255d 2023-08-04 jrmu (list 'caar caar)
421 665c255d 2023-08-04 jrmu (list 'cadr cadr)
422 665c255d 2023-08-04 jrmu (list 'cddr cddr)
423 665c255d 2023-08-04 jrmu (list 'cons cons)
424 665c255d 2023-08-04 jrmu (list 'null? null?)
425 665c255d 2023-08-04 jrmu (list '* *)
426 665c255d 2023-08-04 jrmu (list '/ /)
427 665c255d 2023-08-04 jrmu (list '+ +)
428 665c255d 2023-08-04 jrmu (list '- -)
429 665c255d 2023-08-04 jrmu (list '= =)
430 665c255d 2023-08-04 jrmu (list '< <)
431 665c255d 2023-08-04 jrmu (list '> >)
432 665c255d 2023-08-04 jrmu (list '<= <=)
433 665c255d 2023-08-04 jrmu (list '>= >=)
434 665c255d 2023-08-04 jrmu (list 'remainder remainder)
435 665c255d 2023-08-04 jrmu (list 'eq? eq?)
436 665c255d 2023-08-04 jrmu (list 'equal? equal?)
437 665c255d 2023-08-04 jrmu (list 'display display)))
438 665c255d 2023-08-04 jrmu (define (primitive-procedure-names)
440 665c255d 2023-08-04 jrmu primitive-procedures))
441 665c255d 2023-08-04 jrmu (define (primitive-procedure-objects)
442 665c255d 2023-08-04 jrmu (map (lambda (proc) (list 'primitive (cadr proc)))
443 665c255d 2023-08-04 jrmu primitive-procedures))
444 665c255d 2023-08-04 jrmu (define (apply-primitive-procedure proc args)
445 665c255d 2023-08-04 jrmu (apply-in-underlying-scheme
446 665c255d 2023-08-04 jrmu (primitive-implementation proc) args))
448 665c255d 2023-08-04 jrmu ;; driver-loop
449 665c255d 2023-08-04 jrmu (define input-prompt ";;; M-Eval input:")
450 665c255d 2023-08-04 jrmu (define output-prompt ";;; M-Eval value:")
451 665c255d 2023-08-04 jrmu (define (driver-loop)
452 665c255d 2023-08-04 jrmu (prompt-for-input input-prompt)
453 665c255d 2023-08-04 jrmu (let ((input (read)))
454 665c255d 2023-08-04 jrmu (let ((output (eval input the-global-environment)))
455 665c255d 2023-08-04 jrmu (announce-output output-prompt)
456 665c255d 2023-08-04 jrmu (user-print output)))
457 665c255d 2023-08-04 jrmu (driver-loop))
458 665c255d 2023-08-04 jrmu (define (prompt-for-input string)
459 665c255d 2023-08-04 jrmu (newline) (newline) (display string) (newline))
461 665c255d 2023-08-04 jrmu (define (announce-output string)
462 665c255d 2023-08-04 jrmu (newline) (display string) (newline))
463 665c255d 2023-08-04 jrmu (define (user-print object)
464 665c255d 2023-08-04 jrmu (if (compound-procedure? object)
465 665c255d 2023-08-04 jrmu (display (list 'compound-procedure
466 665c255d 2023-08-04 jrmu (procedure-parameters object)
467 665c255d 2023-08-04 jrmu (procedure-body object)
468 665c255d 2023-08-04 jrmu '<procedure-env>))
469 665c255d 2023-08-04 jrmu (display object)))
470 665c255d 2023-08-04 jrmu (define (setup-environment)
471 665c255d 2023-08-04 jrmu (let ((initial-env
472 665c255d 2023-08-04 jrmu (extend-environment (primitive-procedure-names)
473 665c255d 2023-08-04 jrmu (primitive-procedure-objects)
474 665c255d 2023-08-04 jrmu the-empty-environment)))
475 665c255d 2023-08-04 jrmu (define-variable! 'true true initial-env)
476 665c255d 2023-08-04 jrmu (define-variable! 'false false initial-env)
477 665c255d 2023-08-04 jrmu initial-env))
478 665c255d 2023-08-04 jrmu (define the-global-environment (setup-environment))
480 665c255d 2023-08-04 jrmu ;; auxiliary
481 665c255d 2023-08-04 jrmu (define (test-case actual expected)
483 665c255d 2023-08-04 jrmu (display "Actual: ")
484 665c255d 2023-08-04 jrmu (display actual)
486 665c255d 2023-08-04 jrmu (display "Expected: ")
487 665c255d 2023-08-04 jrmu (display expected)
489 665c255d 2023-08-04 jrmu (define (geval exp) ;; eval globally
490 665c255d 2023-08-04 jrmu (eval exp the-global-environment))
491 665c255d 2023-08-04 jrmu (define (test-eval exp expected)
492 665c255d 2023-08-04 jrmu (test-case (geval exp) expected))
503 665c255d 2023-08-04 jrmu ;; test-suite
505 665c255d 2023-08-04 jrmu ;; procedure definitions
508 665c255d 2023-08-04 jrmu '(define (assoc key records)
509 665c255d 2023-08-04 jrmu (cond ((null? records) false)
510 665c255d 2023-08-04 jrmu ((equal? key (caar records)) (car records))
511 665c255d 2023-08-04 jrmu (else (assoc key (cdr records))))))
514 665c255d 2023-08-04 jrmu '(define (map proc list)
515 665c255d 2023-08-04 jrmu (if (null? list)
517 665c255d 2023-08-04 jrmu (cons (proc (car list))
518 665c255d 2023-08-04 jrmu (map proc (cdr list))))))
521 665c255d 2023-08-04 jrmu '(define (accumulate op initial sequence)
522 665c255d 2023-08-04 jrmu (if (null? sequence)
524 665c255d 2023-08-04 jrmu (op (car sequence)
525 665c255d 2023-08-04 jrmu (accumulate op initial (cdr sequence))))))
527 665c255d 2023-08-04 jrmu ;; all special forms
528 665c255d 2023-08-04 jrmu (test-eval '(begin 5 6) 6)
529 665c255d 2023-08-04 jrmu (test-eval '10 10)
530 665c255d 2023-08-04 jrmu (geval '(define x 3))
531 665c255d 2023-08-04 jrmu (test-eval 'x 3)
532 665c255d 2023-08-04 jrmu (test-eval '(set! x -25) 'ok)
533 665c255d 2023-08-04 jrmu (test-eval 'x -25)
534 665c255d 2023-08-04 jrmu (geval '(define z (lambda (x y) (+ x (* x y)))))
535 665c255d 2023-08-04 jrmu (test-eval '(z 3 4) 15)
536 665c255d 2023-08-04 jrmu (test-eval '(cond ((= x -2) 'x=-2)
537 665c255d 2023-08-04 jrmu ((= x -25) 'x=-25)
538 665c255d 2023-08-04 jrmu (else 'failed))
540 665c255d 2023-08-04 jrmu (test-eval '(if true false true) false)
542 665c255d 2023-08-04 jrmu '(let ((x 4) (y 7))
543 665c255d 2023-08-04 jrmu (+ x y (* x y)))
544 665c255d 2023-08-04 jrmu (+ 4 7 (* 4 7)))
548 665c255d 2023-08-04 jrmu (geval '(define x (+ 3 8)))
549 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x) 11)
550 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x false) false)
551 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x (set! x -2) false) false)
552 665c255d 2023-08-04 jrmu (test-eval 'x -2)
553 665c255d 2023-08-04 jrmu (test-eval '(and 0 true x false (set! x -5)) false)
554 665c255d 2023-08-04 jrmu (test-eval 'x -2)
555 665c255d 2023-08-04 jrmu (test-eval '(or false (set! x 25)) 'ok)
556 665c255d 2023-08-04 jrmu (test-eval 'x 25)
557 665c255d 2023-08-04 jrmu (test-eval '(or (set! x 2) (set! x 4)) 'ok)
558 665c255d 2023-08-04 jrmu (test-eval 'x 2)
559 665c255d 2023-08-04 jrmu (test-eval '(or false (set! x 25) true false) 'ok)
560 665c255d 2023-08-04 jrmu (test-eval 'x 25)
561 665c255d 2023-08-04 jrmu (test-eval '(or ((lambda (x) x) 5)) 5)
562 665c255d 2023-08-04 jrmu (test-eval '(or (begin (set! x (+ x 1)) x)) 26)
568 665c255d 2023-08-04 jrmu '(cond ((assoc 'b '((a 1) (b 2))) => cadr)
569 665c255d 2023-08-04 jrmu (else false))
573 665c255d 2023-08-04 jrmu '(cond ((= 3 4) 'not-true)
574 665c255d 2023-08-04 jrmu ((= (* 2 4) 3) 'also-false)
575 665c255d 2023-08-04 jrmu ((map (lambda (x)
576 665c255d 2023-08-04 jrmu (* x (+ x 1)))
577 665c255d 2023-08-04 jrmu '(2 4 1 9))
579 665c255d 2023-08-04 jrmu (lambda (x)
580 665c255d 2023-08-04 jrmu (accumulate + 0 x)))
581 665c255d 2023-08-04 jrmu (else 'never-reach))
583 665c255d 2023-08-04 jrmu ;; '(6 20 2 90)
586 665c255d 2023-08-04 jrmu ;; procedure definition and application
588 665c255d 2023-08-04 jrmu '(define (factorial n)
589 665c255d 2023-08-04 jrmu (if (= n 0)
591 665c255d 2023-08-04 jrmu (* n (factorial (- n 1))))))
592 665c255d 2023-08-04 jrmu (test-eval '(factorial 5) 120)
597 665c255d 2023-08-04 jrmu '(map (lambda (x)
598 665c255d 2023-08-04 jrmu (* x (+ x 1)))
599 665c255d 2023-08-04 jrmu '(2 1 4 2 8 3))
600 665c255d 2023-08-04 jrmu '(6 2 20 6 72 12))
601 665c255d 2023-08-04 jrmu ;; accumulate
604 665c255d 2023-08-04 jrmu '(accumulate + 0 '(1 2 3 4 5))
607 665c255d 2023-08-04 jrmu ;; make-let
609 665c255d 2023-08-04 jrmu (make-let '(x y) '(3 5) '((+ x y)))
616 665c255d 2023-08-04 jrmu '(let ((x 3))
620 665c255d 2023-08-04 jrmu '(let ((x 3)
625 665c255d 2023-08-04 jrmu '(let ((x 3)
627 665c255d 2023-08-04 jrmu (+ (let ((x (+ y 2))
631 665c255d 2023-08-04 jrmu (+ (* 4 3) 3 2))
633 665c255d 2023-08-04 jrmu '(let ((x 6)
634 665c255d 2023-08-04 jrmu (y (let ((x 2))
636 665c255d 2023-08-04 jrmu (z (let ((a (* 3 2)))
645 665c255d 2023-08-04 jrmu '(let* ((x 3)
646 665c255d 2023-08-04 jrmu (y (+ x 2))
647 665c255d 2023-08-04 jrmu (z (+ x y 5)))
656 665c255d 2023-08-04 jrmu '(let* ((x 3))
657 665c255d 2023-08-04 jrmu (let* ((y 5))
662 665c255d 2023-08-04 jrmu '(let* ((x 3)
663 665c255d 2023-08-04 jrmu (y (+ x 1)))
664 665c255d 2023-08-04 jrmu (+ (let* ((x (+ y 2))
668 665c255d 2023-08-04 jrmu (+ (* 6 6) 3 4))
670 665c255d 2023-08-04 jrmu '(let* ((x 6)
671 665c255d 2023-08-04 jrmu (y (let* ((x 2)
672 665c255d 2023-08-04 jrmu (a (let* ((x (* 3 x)))
675 665c255d 2023-08-04 jrmu (z (+ x y)))
679 665c255d 2023-08-04 jrmu ;; named-let
682 665c255d 2023-08-04 jrmu '(let eight ()
688 665c255d 2023-08-04 jrmu '(let loop ((count 0))
689 665c255d 2023-08-04 jrmu (if (= 100 count)
691 665c255d 2023-08-04 jrmu (loop (+ count 1))))
694 665c255d 2023-08-04 jrmu '(define (prime? x)
695 665c255d 2023-08-04 jrmu (let prime-iter ((i 2))
696 665c255d 2023-08-04 jrmu (cond ((> (* i i) x) true)
697 665c255d 2023-08-04 jrmu ((= (remainder x i) 0) false)
698 665c255d 2023-08-04 jrmu (else (prime-iter (+ i 1)))))))
700 665c255d 2023-08-04 jrmu '(let primes ((x 2)
702 665c255d 2023-08-04 jrmu (cond ((= n 0) '())
703 665c255d 2023-08-04 jrmu ((prime? x)
705 665c255d 2023-08-04 jrmu (primes (+ x 1) (- n 1))))
706 665c255d 2023-08-04 jrmu (else (primes (+ x 1) n))))
707 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))
710 665c255d 2023-08-04 jrmu '(define (fib n)
711 665c255d 2023-08-04 jrmu (let fib-iter ((a 1)
714 665c255d 2023-08-04 jrmu (if (= count 0)
716 665c255d 2023-08-04 jrmu (fib-iter (+ a b) a (- count 1))))))
717 665c255d 2023-08-04 jrmu (test-eval '(fib 19) 4181)
721 665c255d 2023-08-04 jrmu '(let ((y 0))
722 665c255d 2023-08-04 jrmu (do ((x 0 (+ x 1)))
723 665c255d 2023-08-04 jrmu ((= x 5) y)
724 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
735 665c255d 2023-08-04 jrmu '(let ((y 0))
737 665c255d 2023-08-04 jrmu ((= y 5) y)
738 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
742 665c255d 2023-08-04 jrmu '(do ((y '(1 2 3 4)))
743 665c255d 2023-08-04 jrmu ((null? y))
744 665c255d 2023-08-04 jrmu (set! y (cdr y)))
747 665c255d 2023-08-04 jrmu '(let ((y 0))
748 665c255d 2023-08-04 jrmu (do ((x 0 (+ x 1)))
749 665c255d 2023-08-04 jrmu ((= x 5) y)
750 665c255d 2023-08-04 jrmu (set! y (+ y 1))))
753 665c255d 2023-08-04 jrmu '(let ((x '(1 3 5 7 9)))
754 665c255d 2023-08-04 jrmu (do ((x x (cdr x))
755 665c255d 2023-08-04 jrmu (sum 0 (+ sum (car x))))
756 665c255d 2023-08-04 jrmu ((null? x) sum)))
759 665c255d 2023-08-04 jrmu '(let ((z '()))
760 665c255d 2023-08-04 jrmu (do ((x '(1 2 3 4) (cdr x))
761 665c255d 2023-08-04 jrmu (y '(1 2 3 4 5 6 7 8) (cddr y)))
762 665c255d 2023-08-04 jrmu ((null? x) y x z)
763 665c255d 2023-08-04 jrmu (set! z (cons (car x) z))))
764 665c255d 2023-08-04 jrmu '(4 3 2 1))
768 665c255d 2023-08-04 jrmu ;; make-unbound!
769 665c255d 2023-08-04 jrmu ;; broken now due to scan-out-defines
771 665c255d 2023-08-04 jrmu ;; (test-eval
772 665c255d 2023-08-04 jrmu ;; '(let ((x 3))
773 665c255d 2023-08-04 jrmu ;; (let ((x 5))
774 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
775 665c255d 2023-08-04 jrmu ;; (* x x)))
778 665c255d 2023-08-04 jrmu ;; (test-eval
779 665c255d 2023-08-04 jrmu ;; '(let ((x 3))
780 665c255d 2023-08-04 jrmu ;; (let ((x 5))
781 665c255d 2023-08-04 jrmu ;; (define y x)
782 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
783 665c255d 2023-08-04 jrmu ;; (* y x)))
786 665c255d 2023-08-04 jrmu ;; (test-eval
787 665c255d 2023-08-04 jrmu ;; '(let ((y -1) (x 3))
788 665c255d 2023-08-04 jrmu ;; (let ((y 0.5) (x 5))
789 665c255d 2023-08-04 jrmu ;; (define a x)
790 665c255d 2023-08-04 jrmu ;; (define b y)
791 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
792 665c255d 2023-08-04 jrmu ;; (make-unbound! y)
793 665c255d 2023-08-04 jrmu ;; (* a b x y)))
794 665c255d 2023-08-04 jrmu ;; (* 5 3 -1 0.5))
796 665c255d 2023-08-04 jrmu ;; (test-eval
797 665c255d 2023-08-04 jrmu ;; '(let ((x 3) (y 4))
798 665c255d 2023-08-04 jrmu ;; (let ((x 5))
799 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
800 665c255d 2023-08-04 jrmu ;; (+ x 4)))
803 665c255d 2023-08-04 jrmu ;; (test-eval
804 665c255d 2023-08-04 jrmu ;; '(let ((a 1) (b 2) (c 3) (d 4))
805 665c255d 2023-08-04 jrmu ;; (make-unbound! b)
806 665c255d 2023-08-04 jrmu ;; (+ a c d))
807 665c255d 2023-08-04 jrmu ;; (+ 1 3 4))
809 665c255d 2023-08-04 jrmu ;; (test-eval
810 665c255d 2023-08-04 jrmu ;; '(let ((x 4) (y 5))
811 665c255d 2023-08-04 jrmu ;; (let ((a 1) (b 2) (c 3))
812 665c255d 2023-08-04 jrmu ;; (let ((x (+ a b)) (y (+ c a)))
813 665c255d 2023-08-04 jrmu ;; (make-unbound! x)
814 665c255d 2023-08-04 jrmu ;; (let ((a x) (b (+ x y)))
815 665c255d 2023-08-04 jrmu ;; (define z b)
816 665c255d 2023-08-04 jrmu ;; (make-unbound! b)
817 665c255d 2023-08-04 jrmu ;; (* (+ a z)
818 665c255d 2023-08-04 jrmu ;; (+ a b y))))))
819 665c255d 2023-08-04 jrmu ;; (* (+ 4 8)
820 665c255d 2023-08-04 jrmu ;; (+ 4 2 4)))
822 665c255d 2023-08-04 jrmu ;; x 3 -- y 4
823 665c255d 2023-08-04 jrmu ;; x 4 -- y 4
824 665c255d 2023-08-04 jrmu ;; a 4 -- b 4
825 665c255d 2023-08-04 jrmu ;; a 4 -- b 2
827 665c255d 2023-08-04 jrmu ;; scan-out-defines
830 665c255d 2023-08-04 jrmu '(define (f x)
831 665c255d 2023-08-04 jrmu (define (even? n)
832 665c255d 2023-08-04 jrmu (if (= n 0)
834 665c255d 2023-08-04 jrmu (odd? (- n 1))))
835 665c255d 2023-08-04 jrmu (define (odd? n)
836 665c255d 2023-08-04 jrmu (if (= n 0)
838 665c255d 2023-08-04 jrmu (even? (- n 1))))
839 665c255d 2023-08-04 jrmu (even? x)))
840 665c255d 2023-08-04 jrmu (test-eval '(f 5) false)
841 665c255d 2023-08-04 jrmu (test-eval '(f 10) true)
844 665c255d 2023-08-04 jrmu ;; '(let ((x 5))
845 665c255d 2023-08-04 jrmu ;; (define y x)
846 665c255d 2023-08-04 jrmu ;; (define x 3)
847 665c255d 2023-08-04 jrmu ;; (+ x y)))
848 665c255d 2023-08-04 jrmu ;; signal an error because x is undefined if variables are scanned out
