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Exercise_5_26.rkt
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Exercise_5_26.rkt
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#lang racket/base
(require compatibility/mlist)
;; =====================================================
;; Metacircular evaluator
;; =====================================================
(define (true? x) (not (eq? x #f)))
(define (false? x) (eq? x #f))
(define (self-evaluating? exp)
(cond [(number? exp) #t]
[(string? exp) #t]
[else #f]))
(define (variable? exp) (symbol? exp))
(define (quoted? exp) (tagged-list? exp 'quote))
(define (text-of-quotation exp) (cadr exp))
(define (tagged-list? exp tag)
(cond [(pair? exp) (eq? (car exp) tag)]
[(mpair? exp) (eq? (mcar exp) tag)]
[else #f]))
(define (assignment? exp) (tagged-list? exp 'set!))
(define (assignment-variable exp) (cadr exp))
(define (assignment-value exp) (caddr exp))
(define (definition? exp)
(tagged-list? exp 'define))
(define (definition-variable exp)
(if (symbol? (cadr exp))
(cadr exp)
(caadr exp)))
(define (definition-value exp)
(if (symbol? (cadr exp))
(caddr exp)
(make-lambda (cdadr exp) ;; formal parameters
(cddr exp)))) ;; body
(define (lambda? exp) (tagged-list? exp 'lambda))
(define (lambda-parameters exp) (cadr exp))
(define (lambda-body exp) (cddr exp))
(define (make-lambda parameters body)
(cons 'lambda (cons parameters body)))
(define (if? exp) (tagged-list? exp 'if))
(define (if-predicate exp) (cadr exp))
(define (if-consequent exp) (caddr exp))
(define (if-alternative exp)
(if (not (null? (cdddr exp)))
(cadddr exp)
'false))
(define (make-if predicate consequent alternative)
(list 'if predicate consequent alternative))
(define (begin? exp) (tagged-list? exp 'begin))
(define (begin-actions exp) (cdr exp))
(define (last-exp? seq) (null? (cdr seq)))
(define (first-exp seq) (car seq))
(define (rest-exps seq) (cdr seq))
(define (sequence->exp seq)
(cond [(null? seq) seq]
[(last-exp? seq) (first-exp seq)]
[else (make-begin seq)]))
(define (make-begin seq) (cons 'begin seq))
(define (application? exp) (pair? exp))
(define (operator exp) (car exp))
(define (operands exp) (cdr exp))
(define (no-operands? ops) (null? ops))
(define (first-operand ops) (car ops))
(define (rest-operands ops) (cdr ops))
(define (cond? exp) (tagged-list? exp 'cond))
(define (cond-clauses exp) (cdr exp))
(define (cond-else-clause? clause)
(eq? (cond-predicate clause) 'else))
(define (cond-predicate clause) (car clause))
(define (cond-actions clause) (cdr clause))
(define (cond->if exp) (expand-clauses (cond-clauses exp)))
(define (expand-clauses clauses)
(if (null? clauses)
'false ;; no else clause
(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 (primitive-procedure? proc)
(tagged-list? proc 'primitive))
(define (primitive-implementation proc) (cadr proc))
(define primitive-procedures
(list (list 'car car)
(list 'cdr cdr)
(list 'cons cons)
(list 'null? null?)
(list 'list list)
(list '+ +)
(list '- -)
(list '* *)
(list '/ /)
(list '= =)
(list '> >)
(list '< <)))
(define (primitive-procedure-names)
(map car primitive-procedures))
(define (primitive-procedure-objects)
(map (lambda (proc) (list 'primitive (cadr proc)))
primitive-procedures))
(define apply-in-underlying-scheme apply)
(define (apply-primitive-procedure proc args)
(apply-in-underlying-scheme
(primitive-implementation proc) args))
(define (make-procedure parameters body env)
(list 'procedure parameters body env))
(define (compound-procedure? p)
(tagged-list? p 'procedure))
(define (procedure-parameters p) (cadr p))
(define (procedure-body p) (caddr p))
(define (procedure-environment p) (cadddr p))
(define (enclosing-environment env) (cdr env))
(define (first-frame env) (car env))
(define the-empty-environment '())
(define (mmap proc . args)
(if (null? (car args))
null
(mcons
(apply proc (map car args))
(apply mmap
(cons proc (map cdr args))))))
(define (make-frame variables values)
(mmap mcons variables values))
(define (add-binding-to-frame! var val frame)
(mappend! frame (mlist (mcons var val))))
(define (frame-unit-variable unit) (mcar unit))
(define (frame-unit-value unit) (mcdr unit))
(define (travsersing-env end-frame-proc find-proc end-env-proc env var)
(define (env-loop env)
(define (scan pairs)
(let ([current-pair
(if (mpair? pairs)
(mcar pairs)
null)])
(cond [(null? current-pair)
(end-frame-proc env)]
[(eq? var (frame-unit-variable current-pair))
(find-proc current-pair)]
[else (scan (mcdr pairs))])))
(if (eq? env the-empty-environment)
(end-env-proc var)
(scan (first-frame env))))
(env-loop env))
(define (set-variable-value! var val env)
(travsersing-env
(lambda (env) (set-variable-value! var val (enclosing-environment env)))
(lambda (current-pair) (set-mcdr! current-pair val))
(lambda (var) (error "Unbound variable: SET!" var))
env
var))
(define (define-variable! var val env)
(travsersing-env
(lambda (env) (add-binding-to-frame! var val (first-frame env)))
(lambda (current-pair) (set-mcdr! current-pair val))
(lambda (var) (error "Empty environment" var))
env
var))
(define (lookup-variable-value var env)
(travsersing-env
(lambda (env) (lookup-variable-value var (enclosing-environment env)))
(lambda (current-pair) (frame-unit-value current-pair))
(lambda (var) (error "Unbound variable" var))
env
var))
(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 (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))
(define the-global-environment (setup-environment))
(define (prompt-for-input string)
(newline) (newline) (display string) (newline))
(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)))
;; =====================================================
;; Register-Machine simulator
;; =====================================================
(define (make-machine register-names ops controller-text)
(let ([machine (make-new-machine)])
(for-each
(lambda (register-name)
((machine 'allocate-register) register-name))
register-names)
((machine 'install-operations) ops)
((machine 'install-instruction-sequence)
(assemble controller-text machine))
machine))
(define (make-register name)
(let ([contents '*unassigned*])
(define (dispatch message)
(cond [(eq? message 'get) contents]
[(eq? message 'set)
(lambda (value) (set! contents value))]
[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)
'done)
(define (print-statistics)
(newline)
(displayln (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 (make-new-machine)
(let ([pc (make-register 'pc)]
[flag (make-register 'flag)]
[stack (make-stack)]
[the-instruction-sequence '()])
(let ([the-ops
(list (list 'initialize-stack
(lambda () (stack 'initialize)))
(list 'print-stack-statistics
(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)
(error "Unknown register:" name))))
(define (execute)
(let ([insts (get-contents pc)])
(if (null? insts)
'done
(begin
((instruction-execution-proc (car insts)))
(execute)))))
(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]
[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 (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)
(begin
(duplicate-label? next-inst labels)
(receive insts
(cons (make-label-entry next-inst
insts)
labels)))
(receive (cons (make-instruction next-inst)
insts)
labels)))))))
(define (duplicate-label? label-name labels)
(when (assoc label-name labels)
(error "Duplicated label: ASSEMBLE"
label-name)))
(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) (mcons text null))
(define (instruction-text inst) (mcar inst))
(define (instruction-execution-proc inst) (mcdr inst))
(define (set-instruction-execution-proc! inst proc)
(set-mcdr! 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)]
[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 () ; execution procedure for assign
(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 (or (register-exp? e) (constant-exp? e))
(make-primitive-exp e machine labels)
(error "Invalid operation argument: ASSEMBLE")))
(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 (empty-arglist) '())
(define (adjoin-arg arg arglist) (append arglist (list arg)))
(define (last-operand? ops) (null? (cdr ops)))
(define (get-global-environment) the-global-environment)
(define eceval-operations
(list (list 'prompt-for-input prompt-for-input) ;; read-eval-print-loop
(list 'read read)
(list 'get-global-environment get-global-environment)
(list 'announce-output announce-output)
(list 'user-print user-print)
;; eval-dispatch
(list 'self-evaluating? self-evaluating?)
(list 'variable? variable?)
(list 'quoted? quoted?)
(list 'assignment? assignment?)
(list 'definition? definition?)
(list 'if? if?)
(list 'lambda? lambda?)
(list 'begin? begin?)
(list 'application? application?)
;; ev-variable
(list 'lookup-variable-value lookup-variable-value)
;; ev-quoted
(list 'text-of-quotation text-of-quotation)
;; ev-lambda
(list 'lambda-parameters lambda-parameters)
(list 'lambda-body lambda-body)
(list 'make-procedure make-procedure)
;; ev-application
(list 'operands operands)
(list 'operator operator)
;; ev-appl-did-operator
(list 'empty-arglist empty-arglist)
(list 'no-operands? no-operands?)
;; ev-appl-operand-loop
(list 'first-operand first-operand)
(list 'last-operand? last-operand?)
;; ev-appl-accumulate-arg
(list 'adjoin-arg adjoin-arg)
(list 'rest-operands rest-operands)
;; apply-dispatch
(list 'primitive-procedure? primitive-procedure?)
(list 'compound-procedure? compound-procedure?)
;; primitive-apply
(list 'apply-primitive-procedure apply-primitive-procedure)
;; compound-apply
(list 'procedure-parameters procedure-parameters)
(list 'procedure-environment procedure-environment)
(list 'extend-environment extend-environment)
(list 'procedure-body procedure-body)
;; ev-begin
(list 'begin-actions begin-actions)
;; ev-sequence
(list 'first-exp first-exp)
(list 'last-exp? last-exp?)
;; ev-sequence-continue
(list 'rest-exps rest-exps)
;; ev-if
(list 'if-predicate if-predicate)
;; ev-if-decide
(list 'true? true?)
;; ev-if-alternative
(list 'if-alternative if-alternative)
;; ev-if-consequent
(list 'if-consequent if-consequent)
;; ev-assignment
(list 'assignment-variable assignment-variable)
(list 'assignment-value assignment-value)
;; ev-assignment-1
(list 'set-variable-value! set-variable-value!)
;; ev-definition
(list 'definition-variable definition-variable)
(list 'definition-value definition-value)
;; ev-definition-1
(list 'define-variable! define-variable!)))
(define eceval
(make-machine
'(exp env val proc argl continue unev)
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-statistics)) ;; added instruction
(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) ;; clean up stack (from apply-dispatch)
(assign val (const unknown-procedure-type-error))
(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 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))
(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) ;; the operands
(restore env)
(assign argl (op empty-arglist))
(assign proc (reg val)) ;; the operator
(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
(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 expression for later
(save env)
(save continue)
(assign continue (label ev-if-decide))
(assign exp (op if-predicate) (reg exp))
(goto (label eval-dispatch)) ;; evaluate the predicate
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) ;; save variable for later
(assign exp (op assignment-value) (reg exp)) (save env)
(save continue)
(assign continue (label ev-assignment-1))
(goto (label eval-dispatch)) ;; evaluate the assignment value
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) ;; save variable for later
(assign exp (op definition-value) (reg exp))
(save env)
(save continue)
(assign continue (label ev-definition-1))
(goto (label eval-dispatch)) ;; evaluate the definition value
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)))))
(start eceval)
;;EC-Eval input:
;; (define (factorial n)
;; (define (iter product counter)
;; (if (> counter n)
;; product
;; (iter (* counter product)
;; (+ counter 1))))
;; (iter 1 1))
;; (total-pushes = 3 maximum-depth = 3)
;;EC-Eval value:
;; ok
;;EC-Eval input:
;; (factorial 1)
;; (total-pushes = 64 maximum-depth = 10)
;;EC-Eval value:
;; 1
;;EC-Eval input:
;; (factorial 2)
;; (total-pushes = 99 maximum-depth = 10)
;;EC-Eval value:
;; 2
;;EC-Eval input:
;; (factorial 3)
;; (total-pushes = 134 maximum-depth = 10)
;;EC-Eval value:
;; 6
;;EC-Eval input:
;; (factorial 4)
;; (total-pushes = 169 maximum-depth = 10)
;;EC-Eval value:
;; 24
;; total-pushes = 35 * n + 29