計算機プログラムの構造と解釈[第2版]
(翔泳社)
ハロルド エイブルソン (著)ジュリー サスマン (著)
ジェラルド・ジェイ サスマン (著)
Harold Abelson (原著)Julie Sussman (原著)
Gerald Jay Sussman (原著)和田 英一 (翻訳)
開発環境
- OS X Yosemite - Apple (OS)
- Emacs (CUI)、BBEdit - Bare Bones Software, Inc. (GUI) (Text Editor)
- Scheme (プログラミング言語)
- Gauche (処理系)
計算機プログラムの構造と解釈[第2版](ハロルド エイブルソン (著)、ジュリー サスマン (著)、ジェラルド・ジェイ サスマン (著)、Harold Abelson (原著)、Julie Sussman (原著)、Gerald Jay Sussman (原著)、和田 英一 (翻訳)、翔泳社、原書: Structure and Interpretation of Computer Programs (MIT Electrical Engineering and Computer Science)(SICP))の5(レジスタ計算機での計算)、5.4(積極制御評価器)、5.4.4(評価の実行)、評価器の性能監視、問題 5.30-b.を解いてみる。
その他参考書籍
- Instructor's Manual to Accompany Structure & Interpretation of Computer Programs
- プログラミングGauche (Kahuaプロジェクト (著), 川合 史朗 (監修), オライリージャパン)
- Scheme手習い
問題 5.30-b.
コード(BBEdit, Emacs)
eceval30_b.scm
#!/usr/bin/env gosh
;; -*- coding: utf-8 -*-
(load "./simulator.scm")
(load "./operations30_b.scm")
(define (initialize-stack)
(eceval 'initialize-stack))
(define eceval-operations
(list (list 'self-evaluating? self-evaluating?)
(list 'initialize-stack initialize-stack)
(list 'prompt-for-input prompt-for-input)
(list 'read read)
(list 'get-global-environment get-global-environment)
(list 'announce-output announce-output)
(list 'user-print user-print)
(list 'variable? variable?)
(list 'quoted? quoted?)
(list 'assignment? assignment?)
(list 'assignment-value assignment-value)
(list 'definition? definition?)
(list 'if? if?)
(list 'lambda? lambda?)
(list 'begin? begin?)
(list 'cond? cond?)
(list 'let? let?)
(list 'application? application?)
(list 'lookup-variable-value lookup-variable-value)
(list 'text-of-quotation text-of-quotation)
(list 'lambda-parameters lambda-parameters)
(list 'lambda-body lambda-body)
(list 'make-procedure make-procedure)
(list 'operands operands)
(list 'operator operator)
(list 'empty-arglist empty-arglist)
(list 'no-operands? no-operands?)
(list 'first-operand first-operand)
(list 'last-operand? last-operand?)
(list 'adjoin-arg adjoin-arg)
(list 'rest-operands rest-operands)
(list 'primitive-procedure? primitive-procedure?)
(list 'compound-procedure? compound-procedure?)
(list 'apply-primitive-procedure apply-primitive-procedure)
(list 'procedure-parameters procedure-parameters)
(list 'procedure-environment procedure-environment)
(list 'extend-environment extend-environment)
(list 'procedure-body procedure-body)
(list 'begin-actions begin-actions)
(list 'first-exp first-exp)
(list 'last-exp? last-exp?)
(list 'rest-exps rest-exps)
(list 'if-predicate if-predicate)
(list 'true? true?)
(list 'if-alternative if-alternative)
(list 'if-consequent if-consequent)
(list 'assignment-variable assignment-variable)
(list 'set-variable-value! set-variable-value!)
(list 'definition-variable definition-variable)
(list 'definition-value definition-value)
(list 'define-variable! define-variable!)
(list 'cond->if cond->if)
(list 'let->combination let->combination)
(list 'unbound-variable? unbound-variable?)
(list 'check-arguments check-arguments)
))
(define eceval
(make-machine
eceval-operations
'(read-eval-print-loop
(perform (op initialize-stack))
(perform
(op prompt-for-input) (const ";;; EC-Eval input:"))
(assign exp (op read))
(assign env (op get-global-environment))
(assign continue (label print-result))
(goto (label eval-dispatch))
print-result
(perform (op print-stack-statisstics)) ; 性能監視
(perform
(op announce-output) (const ";;; EC-Eval value:"))
(perform (op user-print) (reg val))
(goto (label read-eval-print-loop))
unknown-expression-type
(assign val (const unknown-expression-type-error))
(goto (label signal-error))
unknown-procedure-type
(restore continue)
(assign val (const unknown-procedure-type-error))
(goto (label signal-error))
arguments-error
(assign val (const arguments-error))
(goto (label signal-error))
unbound-variable
(restore continue)
(assign val (const unbound-variable))
(goto (label signal-error))
signal-error
(perform (op user-print) (reg val))
(goto (label read-eval-print-loop))
eval-dispatch
(test (op self-evaluating?) (reg exp))
(branch (label ev-self-eval))
(test (op variable?) (reg exp))
(branch (label ev-variable))
(test (op quoted?) (reg exp))
(branch (label ev-quoted))
(test (op assignment?) (reg exp))
(branch (label ev-assignment))
(test (op definition?) (reg exp))
(branch (label ev-definition))
(test (op if?) (reg exp))
(branch (label ev-if))
(test (op lambda?) (reg exp))
(branch (label ev-lambda))
(test (op begin?) (reg exp))
(branch (label ev-begin))
(test (op cond?) (reg exp))
(branch (label ev-cond))
(test (op let?) (reg exp))
(branch (label ev-let))
(test (op application?) (reg exp))
(branch (label ev-application))
(goto (label unknown-expression-type))
ev-self-eval
(assign val (reg exp))
(goto (reg continue))
ev-variable
(assign val (op lookup-variable-value) (reg exp) (reg env))
(test (op unbound-variable?) (reg val))
(branch (label unbound-variable))
(goto (reg continue))
ev-quoted
(assign val (op text-of-quotation) (reg exp))
(goto (reg continue))
ev-lambda
(assign unev (op lambda-parameters) (reg exp))
(assign exp (op lambda-body) (reg exp))
(assign val (op make-procedure)
(reg unev) (reg exp) (reg env))
(goto (reg continue))
ev-application
(save continue)
(save env)
(assign unev (op operands) (reg exp))
(save unev)
(assign exp (op operator) (reg exp))
(assign continue (label ev-appl-did-operator))
(goto (label eval-dispatch))
ev-appl-did-operator
(restore unev)
(restore env)
(assign argl (op empty-arglist))
(assign proc (reg val))
(test (op no-operands?) (reg unev))
(branch (label apply-dispatch))
(save proc)
ev-appl-operand-loop
(save argl)
(assign exp (op first-operand) (reg unev))
(test (op last-operand?) (reg unev))
(branch (label ev-appl-last-arg))
(save env)
(save unev)
(assign continue (label ev-appl-accumulate-arg))
(goto (label eval-dispatch))
ev-appl-accumulate-arg
(restore unev)
(restore env)
(restore argl)
(assign argl (op adjoin-arg) (reg val) (reg argl))
(assign unev (op rest-operands) (reg unev))
(goto (label ev-appl-operand-loop))
ev-appl-last-arg
(assign continue (label ev-appl-accum-last-arg))
(goto (label eval-dispatch))
ev-appl-accum-last-arg
(restore argl)
(assign argl (op adjoin-arg) (reg val) (reg argl))
(restore proc)
(goto (label apply-dispatch))
apply-dispatch
(test (op primitive-procedure?) (reg proc))
(branch (label primitive-apply))
(test (op compound-procedure?) (reg proc))
(branch (label compound-apply))
(goto (label unknown-procedure-type))
primitive-apply
(test (op check-arguments) (reg proc) (reg argl))
(branch (label arguments-error))
(assign val (op apply-primitive-procedure)
(reg proc)
(reg argl))
(restore continue)
(goto (reg continue))
compound-apply
(assign unev (op procedure-parameters) (reg proc))
(assign env (op procedure-environment) (reg proc))
(assign env (op extend-environment)
(reg unev) (reg argl) (reg env))
(assign unev (op procedure-body) (reg proc))
(goto (label ev-sequence))
ev-begin
(assign unev (op begin-actions) (reg exp))
(save continue)
(goto (label ev-sequence))
ev-sequence
(assign exp (op first-exp) (reg unev))
(test (op last-exp?) (reg unev))
(branch (label ev-sequence-last-exp))
(save unev)
(save env)
(assign continue (label ev-sequence-continue))
(goto (label eval-dispatch))
ev-sequence-continue
(restore env)
(restore unev)
(assign unev (op rest-exps) (reg unev))
(goto (label ev-sequence))
ev-sequence-last-exp
(restore continue)
(goto (label eval-dispatch))
ev-if
(save exp)
(save env)
(save continue)
(assign continue (label ev-if-decide))
(assign exp (op if-predicate) (reg exp))
(goto (label eval-dispatch))
ev-if-decide
(restore continue)
(restore env)
(restore exp)
(test (op true?) (reg val))
(branch (label ev-if-consequent))
ev-if-alternative
(assign exp (op if-alternative) (reg exp))
(goto (label eval-dispatch))
ev-if-consequent
(assign exp (op if-consequent) (reg exp))
(goto (label eval-dispatch))
ev-assignment
(assign unev (op assignment-variable) (reg exp))
(save unev)
(assign exp (op assignment-value) (reg exp))
(save env)
(save continue)
(assign continue (label ev-assignment-1))
(goto (label eval-dispatch))
ev-assignment-1
(restore continue)
(restore env)
(restore unev)
(perform
(op set-variable-value!) (reg unev) (reg val) (reg env))
(assign val (const ok))
(goto (reg continue))
ev-definition
(assign unev (op definition-variable) (reg exp))
(save unev)
(assign exp (op definition-value) (reg exp))
(save env)
(save continue)
(assign continue (label ev-definition-1))
(goto (label eval-dispatch))
ev-definition-1
(restore continue)
(restore env)
(restore unev)
(perform
(op define-variable!) (reg unev) (reg val) (reg env))
(assign val (const ok))
(goto (reg continue))
ev-cond
(assign exp (op cond->if) (reg exp))
(goto (label eval-dispatch))
ev-let
(assign exp (op let->combination) (reg exp))
(goto (label eval-dispatch))
)))
(define the-global-environment (setup-environment))
(start eceval)
simulator.scm
;; -*- coding: utf-8 -*-
(define (tagged-list? exp tag)
(if (pair? exp)
(eq? (car exp) tag)
#f))
(define (make-machine ops controller-text)
(let ((machine (make-new-machine)))
((machine 'install-operations) ops)
((machine 'install-instruction-sequence)
(assemble controller-text machine))
machine))
(define (make-register name)
(let ((contents '*unassigned*)
(trace #f))
(define (dispatch message)
(cond ((eq? message 'get) contents)
((eq? message 'set)
(lambda (value) (set! contents value)))
((eq? message 'trace-on)
(set! trace #t))
((eq? message 'trace-off)
(set! trace #f))
((eq? message 'trace?) trace)
(else
(error "Unknown request -- REGISTER" message))))
dispatch))
(define (get-contents register)
(register 'get))
(define (set-contents! register value)
((register 'set) value))
(define (make-stack)
(let ((s '())
(number-pushes 0)
(max-depth 0)
(current-depth 0))
(define (push x)
(set! s (cons x s))
(set! number-pushes (+ 1 number-pushes))
(set! current-depth (+ 1 current-depth))
(set! max-depth (max current-depth max-depth)))
(define (pop)
(if (null? s)
(error "Empty stack -- POP")
(let ((top (car s)))
(set! s (cdr s))
(set! current-depth (- current-depth 1))
top)))
(define (initialize)
(set! s '())
(set! number-pushes 0)
(set! max-depth 0)
(set! current-depth 0))
(define (print-statistics)
(print (list 'total-pushes '= number-pushes
'maximum-depth '= max-depth)))
(define (dispatch message)
(cond ((eq? message 'push) push)
((eq? message 'pop) (pop))
((eq? message 'initialize) (initialize))
((eq? message 'print-statistics)
(print-statistics))
(else (error "Unknown request -- STACK"
message))))
dispatch))
(define (pop stack)
(stack 'pop))
(define (push stack value)
((stack 'push) value))
(define (print-statistics machine)
((machine 'stack) 'print-statistics))
(define (make-new-machine)
(let ((pc (make-register 'pc))
(flag (make-register 'flag))
(stack (make-stack))
(the-instruction-sequence '())
(instruction-counting 0)
(trace-flag #f)
(label '())
(breakpoints '())
(current-n -1))
(let ((the-ops
(list (list 'initialize-stack
(lambda () (stack 'initialize)))
(list 'print-stack-statisstics
(lambda () (stack 'print-statistics)))))
(register-table
(list (list 'pc pc) (list 'flag flag))))
(define (allocate-register name)
(if (assoc name register-table)
(error "Multiply defined register: " name)
(set! register-table
(cons (list name (make-register name))
register-table)))
'register-allocated)
(define (lookup-register name)
(let ((val (assoc name register-table)))
(if val
(cadr val)
(begin (allocate-register name)
(lookup-register name)))))
(define (execute)
(let ((insts (get-contents pc)))
(if (null? insts)
'done
(begin
(if (eq? (caaar insts) 'label)
(begin (set! label (cadr (caar insts)))
(set! current-n 0))
(set! instruction-counting (+ instruction-counting 1)))
(if trace-flag
(print "label: " label ", trace: " (caar insts)))
(let ((val (assoc label breakpoints)))
(if (and val
(memq current-n (cdr val)))
(print "break label:" label " offset:" current-n)
(begin ((instruction-execution-proc (car insts)))
(set! current-n (+ current-n 1))
(execute))))))))
(define (set-breakpoint label n)
(let ((val (assoc label breakpoints)))
(if val
(set-cdr! val (cons n (cdr val)))
(set! breakpoints (cons (cons label (list n)) breakpoints))))
'done)
(define (proceed-machine)
(let ((insts (get-contents pc)))
(if (null? insts)
'done
(begin
(if (eq? (caaar insts) 'label)
(begin (set! label (cadr (caar insts)))
(set! current-n 0))
(set! instruction-counting (+ instruction-counting 1)))
(if trace-flag
(print "label: " label ", trace: " (caar insts)))
(begin ((instruction-execution-proc (car insts)))
(set! current-n (+ current-n 1))
(execute))))))
(define (cancel-breakpoint label n)
(let ((val (assoc label breakpoints)))
(if val
(set-cdr! val (filter (lambda (i)
(not (= i n)))
(cdr val))))))
(define (dispatch message)
(cond ((eq? message 'start)
(set-contents! pc the-instruction-sequence)
(execute))
((eq? message 'install-instruction-sequence)
(lambda (seq) (set! the-instruction-sequence seq)))
((eq? message 'allocate-register) allocate-register)
((eq? message 'get-register) lookup-register)
((eq? message 'install-operations)
(lambda (ops) (set! the-ops (append the-ops ops))))
((eq? message 'stack) stack)
((eq? message 'operations) the-ops)
((eq? message 'print-instruction-counting)
(print "(instruction-counting = " instruction-counting ")"))
((eq? message 'initialize-instruction-counting)
(set! instruction-counting 0)
'done)
((eq? message 'trace-on) (set! trace-flag #t))
((eq? message 'trace-off) (set! trace-flag #f))
((eq? message 'trace-register-on)
(lambda (reg-name)
(let ((val (lookup-register reg-name)))
(if val
(val 'trace-on)
(error "Unknown register:" reg-name)))))
((eq? message 'trace-register-off)
(lambda (reg-name)
(let ((val (lookup-register reg-name)))
(if val
(val 'trace-off)
(error "Unknown register:" reg-name)))))
((eq? message 'set-breakpoint) set-breakpoint)
((eq? message 'proceed-machine) proceed-machine)
((eq? message 'cancel-breakpoint) cancel-breakpoint)
((eq? message 'cancel-all-breakpoints)
(set! breakpoints '()))
((eq? message initialize-stack) (stack 'initialize))
(else (error "Unknown request -- MACHINE" message))))
dispatch)))
(define (start machine)
(machine 'start))
(define (get-register-contents machine register-name)
(get-contents (get-register machine register-name)))
(define (set-register-contents! machine register-name value)
(set-contents! (get-register machine register-name) value)
'done)
(define (get-register machine reg-name)
((machine 'get-register) reg-name))
(define (print-instruction-counting machine)
(machine 'print-instruction-counting))
(define (initialize-instruction-counting machine)
(machine 'initialize-instruction-counting))
(define (trace-register-on machine register-name)
((machine 'trace-register-on) register-name))
(define (trace-register-off machine register-name)
((machine 'trace-register-off) register-name))
(define (trace-on machine)
(machine 'trace-on))
(define (trace-off machine)
(machine 'trace-off))
(define (set-breakpoint machine label n)
((machine 'set-breakpoint) label n))
(define (proceed-machine machine)
((machine 'proceed-machine)))
(define (cancel-breakpoint machine label n)
((machine 'cancel-breakpoint) label n))
(define (cancel-all-breakpoints machine)
(machine 'cancel-all-breakpoints))
(define (assemble controller-text machine)
(extract-labels controller-text
(lambda (insts labels)
(update-insts! insts labels machine)
insts)))
(define (extract-labels text receive)
(if (null? text)
(receive '() '())
(extract-labels
(cdr text)
(lambda (insts labels)
(let ((next-inst (car text)))
(if (symbol? next-inst)
(if (assoc next-inst labels)
(error "Multiply defined label:" next-inst)
(begin (set! insts (cons (list (list 'label next-inst))
insts))
(receive insts
(cons (make-label-entry next-inst
insts)
labels))))
(receive (cons (make-instruction next-inst)
insts)
labels)))))))
(define (update-insts! insts labels machine)
(let ((pc (get-register machine 'pc))
(flag (get-register machine 'flag))
(stack (machine 'stack))
(ops (machine 'operations)))
(for-each
(lambda (inst)
(set-instruction-execution-proc!
inst
(make-execution-procedure
(instruction-text inst) labels machine
pc flag stack ops)))
insts)))
(define (make-instruction text)
(cons text '()))
(define (instruction-text inst)
(car inst))
(define (instruction-execution-proc inst)
(cdr inst))
(define (set-instruction-execution-proc! inst proc)
(set-cdr! inst proc))
(define (make-label-entry label-name insts)
(cons label-name insts))
(define (lookup-label labels label-name)
(let ((val (assoc label-name labels)))
(if val
(cdr val)
(error "Undefined label -- ASSEMBLE" label-name))))
(define (make-execution-procedure inst labels machine pc flag stack ops)
(cond ((eq? (car inst) 'assign)
(make-assign inst machine labels ops pc))
((eq? (car inst) 'test)
(make-test inst machine labels ops flag pc))
((eq? (car inst) 'branch)
(make-branch inst machine labels flag pc))
((eq? (car inst) 'goto)
(make-goto inst machine labels pc))
((eq? (car inst) 'save)
(make-save inst machine stack pc))
((eq? (car inst) 'restore)
(make-restore inst machine stack pc))
((eq? (car inst) 'perform)
(make-perform inst machine labels ops pc))
((eq? (car inst) 'del)
((make-del inst machine pc)))
((eq? (car inst) 'label)
(lambda () (advance-pc pc)))
(else (error "Unknown instruction type -- ASSEMBLE"
inst))))
(define (make-assign inst machine labels operations pc)
(let ((target
(get-register machine (assign-reg-name inst)))
(value-exp (assign-value-exp inst)))
(let ((value-proc
(if (operation-exp? value-exp)
(make-operation-exp
value-exp machine labels operations)
(make-primitive-exp
(car value-exp) machine labels))))
(lambda ()
(if (target 'trace?)
(print "register-name:" (assign-reg-name inst)
" old:" (get-contents target)
" new:" (value-proc)))
(set-contents! target (value-proc))
(advance-pc pc)))))
(define (assign-reg-name assign-instruction)
(cadr assign-instruction))
(define (assign-value-exp assign-instruction)
(cddr assign-instruction))
(define (advance-pc pc)
(set-contents! pc (cdr (get-contents pc))))
(define (make-test inst machine labels operations flag pc)
(let ((condition (test-condition inst)))
(if (operation-exp? condition)
(let ((condition-proc
(make-operation-exp
condition machine labels operations)))
(lambda ()
(set-contents! flag (condition-proc))
(advance-pc pc)))
(error "Bad TEST instruction -- ASSEMBLE" inst))))
(define (test-condition test-instruction)
(cdr test-instruction))
(define (make-branch inst machine labels flag pc)
(let ((dest (branch-dest inst)))
(if (label-exp? dest)
(let ((insts
(lookup-label labels (label-exp-label dest))))
(lambda ()
(if (get-contents flag)
(set-contents! pc insts)
(advance-pc pc))))
(error "Bad BRANCH instruction -- ASSEMBLE" inst))))
(define (branch-dest branch-instruction)
(cadr branch-instruction))
(define (make-goto inst machine labels pc)
(let ((dest (goto-dest inst)))
(cond ((label-exp? dest)
(let ((insts
(lookup-label labels
(label-exp-label dest))))
(lambda () (set-contents! pc insts))))
((register-exp? dest)
(let ((reg
(get-register machine
(register-exp-reg dest))))
(lambda ()
(set-contents! pc (get-contents reg)))))
(else (error "Bad GOTO instruction -- ASSEMBLE"
inst)))))
(define (goto-dest goto-instruction)
(cadr goto-instruction))
(define (make-save inst machine stack pc)
(let ((reg (get-register machine
(stack-inst-reg-name inst))))
(lambda ()
(push stack (get-contents reg))
(advance-pc pc))))
(define (make-restore inst machine stack pc)
(let ((reg (get-register machine
(stack-inst-reg-name inst))))
(lambda ()
(set-contents! reg (pop stack))
(advance-pc pc))))
(define (stack-inst-reg-name stack-instruction)
(cadr stack-instruction))
(define (make-perform inst machine labels operations pc)
(let ((action (perform-action inst)))
(if (operation-exp? action)
(let ((action-proc
(make-operation-exp
action machine labels operations)))
(lambda ()
(action-proc)
(advance-pc pc)))
(error "Bad PERFORM instruction -- ASSEMBLE" inst))))
(define (perform-action inst) (cdr inst))
(define (make-primitive-exp exp machine labels)
(cond ((constant-exp? exp)
(let ((c (constant-exp-value exp)))
(lambda () c)))
((label-exp? exp)
(let ((insts
(lookup-label labels
(label-exp-label exp))))
(lambda () insts)))
((register-exp? exp)
(let ((r (get-register machine
(register-exp-reg exp))))
(lambda () (get-contents r))))
(else
(error "Unknown expression type -- ASSEMBLE" exp))))
(define (register-exp? exp) (tagged-list? exp 'reg))
(define (register-exp-reg exp) (cadr exp))
(define (constant-exp? exp) (tagged-list? exp 'const))
(define (constant-exp-value exp) (cadr exp))
(define (label-exp? exp) (tagged-list? exp 'label))
(define (label-exp-label exp) (cadr exp))
(define (make-operation-exp exp machine labels operations)
(let ((op (lookup-prim (operation-exp-op exp) operations))
(aprocs
(map (lambda (e)
(if (label-exp? e)
(error "Bad OPERANDS instruction -- ASSEMBLE" e)
(make-primitive-exp e machine labels)))
(operation-exp-operands exp))))
(lambda ()
(apply op (map (lambda (p) (p)) aprocs)))))
(define (operation-exp? exp)
(and (pair? exp) (tagged-list? (car exp) 'op)))
(define (operation-exp-op operation-exp)
(cadr (car operation-exp)))
(define (operation-exp-operands operation-exp)
(cdr operation-exp))
(define (lookup-prim symbol operations)
(let ((val (assoc symbol operations)))
(if val
(cadr val)
(error "Unknown operation -- ASSEMBLE" symbol))))
(define (make-del inst machine pc)
(let ((target
(get-register machine (del-reg-name inst))))
(lambda ()
(set-contents! target '*unassigned*)
(advance-pc pc))))
(define (del-reg-name delete-instruction)
(cadr delete-instruction))
operations30_b.scm
;; -*- coding: utf-8 -*-
(load "./environment30_b.scm")
(define (prompt-for-input string)
(newline) (newline) (display string) (newline))
(define (get-global-environment) the-global-environment)
(define (announce-output string)
(newline) (display string) (newline))
(define (user-print object)
(if (compound-procedure? object)
(display (list 'compound-procedure
(procedure-parameters object)
(procedure-body object)
'<procedure-env>))
(display object)))
(define (self-evaluating? exp)
(cond ((number? exp) #t)
((string? exp) #t)
(else #f)))
(define (variable? exp) (symbol? exp))
(define (unbound-variable? var) (eq? var '*unbound-variable*))
(define (tagged-list? exp tag)
(if (pair? exp)
(eq? (car exp) tag)
#f))
(define (quoted? exp) (tagged-list? exp 'quote))
(define (assignment? exp) (tagged-list? exp 'set!))
(define (definition? exp) (tagged-list? exp 'define))
(define (if? exp) (tagged-list? exp 'if))
(define (lambda? exp) (tagged-list? exp 'lambda))
(define (begin? exp) (tagged-list? exp 'begin))
(define (cond? exp) (tagged-list? exp 'cond))
(define (let? exp) (tagged-list? exp 'let))
(define (application? exp) (pair? exp))
(define (text-of-quotation exp) (cadr exp))
(define (lambda-parameters exp) (cadr exp))
(define (lambda-body exp) (cddr exp))
(define (make-procedure parameters body env)
(list 'procedure parameters body env))
(define (operands exp) (cdr exp))
(define (operator exp) (car exp))
(define (no-operands? ops) (null? ops))
(define (first-operand ops) (car ops))
(define (empty-arglist) '())
(define (last-operand? ops) (null? (cdr ops)))
(define (adjoin-arg arg arglist) (append arglist (list arg)))
(define (rest-operands ops) (cdr ops))
(define (primitive-procedure? proc) (tagged-list? proc 'primitive))
(define (compound-procedure? p) (tagged-list? p 'procedure))
(define (primitive-implementation proc) (cadr proc))
(define apply-in-underlying-scheme apply)
(define (apply-primitive-procedure proc args)
(apply-in-underlying-scheme
(primitive-implementation proc) args))
(define (procedure-parameters p) (cadr p))
(define (procedure-environment p) (cadddr p))
(define (procedure-body p) (caddr p))
(define (check-arguments proc argl)
(if (or (and (eq? (cadr proc) car)
(not (pair? (car argl))))
(and (eq? (cadr proc) /)
(= (cadr argl) 0)))
#t
#f))
(define (begin-actions exp) (cdr exp))
(define (first-exp seq) (car seq))
(define (last-exp? seq) (null? (cdr seq)))
(define (rest-exps seq) (cdr seq))
(define (if-predicate exp) (cadr exp))
(define (true? x)
(not (eq? x #f)))
(define (if-alternative exp)
(if (not (null? (cdddr exp)))
(cadddr exp)
'false))
(define (if-consequent exp) (caddr exp))
(define (assignment-variable exp) (cadr exp))
(define (assignment-value exp) (caddr exp))
(define (definition-variable exp)
(if (symbol? (cadr exp))
(cadr exp)
(caadr exp)))
(define (make-lambda parameters body)
(cons 'lambda (cons parameters body)))
(define (definition-value exp)
(if (symbol? (cadr exp))
(caddr exp)
(make-lambda (cdadr exp)
(cddr exp))))
(define (make-if predicate consequent alternative)
(list 'if predicate consequent alternative))
(define (sequence->exp seq)
(cond ((null? seq) seq)
((last-exp? seq) (first-exp seq))
(else (make-begin seq))))
(define (expand-clauses clauses)
(if (null? clauses)
'false
(let ((first (car clauses))
(rest (cdr clauses)))
(if (cond-else-clause? first)
(if (null? rest)
(sequence->exp (cond-actions first))
(error "ELSE clause isn't last -- COND->IF" clauses))
(make-if (cond-predicate first)
(sequence->exp (cond-actions first))
(expand-clauses rest))))))
(define (cond->if exp) (expand-clauses (cond-clauses exp)))
(define (let-vars exp) (map car (cadr exp)))
(define (let-exps exp) (map cadr (cadr exp)))
(define (let-body exp) (cddr exp))
(define (let->combination exp)
(cons (make-lambda (let-vars exp)
(let-boy exp))
(let-exps exp)))
(define primitive-procedures
(list (list 'car car)
(list 'cdr cdr)
(list 'cons cons)
(list 'null? null?)
(list 'list list)
(list 'symbol? symbol?)
(list 'exit exit)
(list '= =)
(list '+ +)
(list '- -)
(list '* *)
(list '/ /)
(list '> >)
(list '< <)
(list 'not not)
))
(define (primitive-procedure-names)
(map car primitive-procedures))
(define (primitive-procedure-objects)
(map (lambda (proc)
(list 'primitive (cadr proc)))
primitive-procedures))
(define (setup-environment)
(let ((initial-env
(extend-environment (primitive-procedure-names)
(primitive-procedure-objects)
the-empty-environment)))
(define-variable! 'true #t initial-env)
(define-variable! 'false #f initial-env)
initial-env))
environment30_b.scm
;; -*- coding: utf-8 -*-
(define (enclosing-environment env) (cdr env))
(define (first-frame env) (car env))
(define the-empty-environment '())
(define (make-frame variables values) (cons variables values))
(define (frame-variables frame) (car frame))
(define (frame-values frame) (cdr frame))
(define (add-binding-to-frame! var val frame)
(set-car! frame (cons var (car frame)))
(set-cdr! frame (cons val (cdr frame))))
(define (extend-environment vars vals base-env)
(if (= (length vars) (length vals))
(cons (make-frame vars vals) base-env)
(if (< (length vars) (length vals))
(error "Too many arguments supplied" vars vals)
(error "Too few arguments supplied" vars vals))))
(define (lookup-variable-value var env)
(define (env-loop env)
(define (scan vars vals)
(cond ((null? vars)
(env-loop (enclosing-environment env)))
((eq? var (car vars))
(car vals))
(else (scan (cdr vars) (cdr vals)))))
(if (eq? env the-empty-environment)
'*unbound-variable*
(let ((frame (first-frame env)))
(scan (frame-variables frame)
(frame-values frame)))))
(env-loop env))
(define (set-variable-value! var val env)
(define (env-loop env)
(define (scan vars vals)
(cond ((null? vars)
(env-loop (enclosing-environment env)))
((eq? var (car vars))
(set-car! vals val))
(else (scan (cdr vars) (cdr vals)))))
(if (eq? env the-empty-environment)
(error "Unbound variable -- SET!" var)
(let ((frame (first-frame env)))
(scan (frame-variables frame)
(frame-values frame)))))
(env-loop env))
(define (define-variable! var val env)
(let ((frame (first-frame env)))
(define (scan vars vals)
(cond ((null? vars)
(add-binding-to-frame! var val frame))
((eq? var (car vars))
(set-car! vals val))
(else (scan (cdr vars) (cdr vals)))))
(scan (frame-variables frame)
(frame-values frame))))
入出力結果(Terminal(gosh), REPL(Read, Eval, Print, Loop))
$ ./eceval30_b.scm ;;; EC-Eval input: (car (cons 1 2)) (total-pushes = 13 maximum-depth = 8) ;;; EC-Eval value: 1 ;;; EC-Eval input: (car 1) arguments-error ;;; EC-Eval input: (/ 1 2) (total-pushes = 8 maximum-depth = 5) ;;; EC-Eval value: 1/2 ;;; EC-Eval input: (/ 1 0) arguments-error ;;; EC-Eval input: (exit) $
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