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amb_evaluator.scm
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amb_evaluator.scm
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;:
;: Amb Evaluator
(load "debug_print.scm")
(load "prime.scm")
(load "grammars.scm")
(load "environment.scm")
(define (ambeval expr env succeed fail)
(display-debug "ambeval: ")
(display-debug expr)
(display-debug " <env> ")
(display-debug succeed)
(display-debug " ")
(display-debug fail)
(newline-debug)
((analyze expr) env succeed fail))
(define (analyze expr)
(cond ((self-evaluating? expr)
(analyze-self-evaluating expr))
((quoted? expr) (analyze-quoted expr))
((variable? expr) (analyze-variable expr))
((assignment? expr) (analyze-assignment expr))
((permanent-assignment? expr) (analyze-perm-assignment expr))
((definition? expr) (analyze-definition expr))
((if? expr) (analyze-if expr))
((lambda? expr) (analyze-lambda expr))
((begin? expr) (analyze-sequence (begin-actions expr)))
((cond? expr) (analyze (cond->if expr)))
((and? expr) (analyze (and->if expr)))
((or? expr) (analyze (or->if expr)))
((let? expr) (analyze-let expr))
((unless? expr) (analyze (unless->if expr)))
((amb? expr) (analyze-amb expr))
((application? expr) (analyze-application expr))
(else
(error-report "Unknown exprression type -- ANALYZE" expr))))
(define (print-analyze msg . objects)
(display-debug msg)
(if (null? objects)
'ok
(display-debug objects))
(newline-debug))
(define (analyze-self-evaluating expr)
(print-analyze "Analyze-self-evaluating <=> " expr)
(lambda (env succeed fail)
(succeed expr fail)))
(define (analyze-quoted expr)
(print-analyze "Before analyze-quoted => " expr)
(let ((qval (text-of-quotation expr)))
(print-analyze "=> After analyze-quoted: lambda (env succeed fail)" qval)
(lambda (env succeed fail)
(succeed qval fail))))
(define (analyze-variable expr)
(print-analyze "Analyze-variable <=> " expr)
(lambda (env succeed fail)
(succeed (lookup-variable-value expr env) fail)))
(define (analyze-lambda expr)
(print-analyze "Before analyze-lambda => " expr)
(let ((vars (lambda-parameters expr))
(bproc (analyze-sequence (lambda-body expr))))
(print-analyze "=> After analyze-lambda: lambda (env succeed fail) " vars bproc)
(lambda (env succeed fail)
(succeed (make-procedure vars bproc env) fail))))
(define (analyze-if expr)
(print-analyze "Before analyze-if => " expr)
(let ((pproc (analyze (if-predicate expr)))
(cproc (analyze (if-consequent expr)))
(aproc (analyze (if-alternative expr))))
(print-analyze "=> After analyze-if: lambda (env succeed fail) " pproc cproc aproc)
(lambda (env succeed fail)
(pproc env
(lambda (pred-value fail2)
(if (true? pred-value)
(cproc env succeed fail2)
(aproc env succeed fail2)))
fail))))
(define (analyze-sequence exprs)
(print-analyze "Before analyze-sequence => " exprs)
(define (sequentially a b)
(lambda (env succeed fail)
(a env
(lambda (a-value fail2)
(b env succeed fail2))
fail)))
(define (loop first-proc rest-procs)
(print-analyze " analyze-sequence loop => first-proc: " first-proc)
(if (null? rest-procs)
(begin (print-analyze "=> After analyze-sequence: " first-proc)
first-proc)
(loop (sequentially first-proc (car rest-procs))
(cdr rest-procs))))
(let ((procs (map analyze exprs)))
(print-analyze " Before analyze-sequence loop => " procs)
(if (null? procs)
(error-report "Empty sequence -- ANALYZE"))
(loop (car procs) (cdr procs))))
(define (analyze-definition expr)
(print-analyze "Before analyze-definition => " expr)
(let ((var (definition-variable expr))
(vproc (analyze (definition-value expr))))
(print-analyze "=> After analyze-definition: lambda (env succeed fail) " var vproc)
(lambda (env succeed fail)
(vproc env
(lambda (val fail2)
(define-variable! var val env)
(succeed 'ok fail2))
fail))))
(define (analyze-assignment expr)
(print-analyze "Before analyze-assignment => " expr)
(let ((var (assignment-variable expr))
(vproc (analyze (assignment-value expr))))
(print-analyze "=> After analyze-assignment: lambda (env) " var vproc)
(lambda (env succeed fail)
(vproc env
(lambda (val fail2)
(let ((old-vlue (lookup-variable-value var env)))
(set-variable-value! var val env)
(succeed 'ok
(lambda ()
(set-variable-value! var old-vlue env)
(fail2)))))
fail))))
(define (permanent-assignment? expr)
(tagged-list? expr 'permanent-set!))
(define (analyze-perm-assignment expr)
(print-analyze "Before analyze-perm-assignment => " expr)
(let ((var (assignment-variable expr))
(vproc (analyze (assignment-value expr))))
(print-analyze "=> After analyze-perm-assignment: lambda (env) " var vproc)
(lambda (env succeed fail)
(vproc env
(lambda (val fail2)
(set-variable-value! var val env)
(succeed 'ok fail2))
fail))))
(define (analyze-let expr)
(print-analyze "Before analyze-let => " expr)
(let ((proc (analyze (let->combination expr))))
(print-analyze "=> After analyze-let: lambda (env succeed fail) " proc)
proc))
;(lambda (env succeed fail)
; (proc env succeed fail))))
(define (analyze-application expr)
(print-analyze "Before analyze-application => " expr)
(let ((fproc (analyze (operator expr)))
(aprocs (map analyze (operands expr))))
(print-analyze "=> After analyze-application: lambda (env succeed fail) " fproc aprocs)
(lambda (env succeed fail)
(fproc env
(lambda (proc fail2)
(get-args aprocs env (lambda (args fail3)
(execute-application proc args succeed fail3))
fail2))
fail))))
(define (get-args aprocs env succeed fail)
(print-analyze "Before get-args => " aprocs)
(if (null? aprocs)
(succeed '() fail)
((car aprocs) env
(lambda (arg fail2)
(get-args (cdr aprocs)
env
(lambda (args fail3)
(print-analyze "=> After get-args: " args)
(succeed (cons arg args) fail3))
fail2))
fail)))
(define (execute-application proc args succeed fail)
(cond ((primitive-procedure? proc)
(succeed (apply-primitive-procedure proc args) fail))
((compound-procedure? proc)
((procedure-body proc)
(extend-environment (procedure-parameters proc)
args
(procedure-environment proc))
succeed
fail))
(else (error-report "Unknown procedure type -- EXECUTE-APPLICATION" proc))))
(define (amb? expr) (tagged-list? expr 'amb))
(define (amb-choices expr) (cdr expr))
(define (analyze-amb expr)
(print-analyze "Before analyze amb => ")
(let ((cprocs (map analyze (amb-choices expr))))
(print-analyze "=> After analyze amb: " cprocs)
(lambda (env succeed fail)
(define (try-next choices)
(if (null? choices)
(fail)
((car choices) env
succeed
(lambda () (try-next (cdr choices))))))
(try-next cprocs))))
(define input-prompt ";;; Amb-Eval input:")
(define output-prompt ";;; Amb-Eval value:")
(define (get-input)
(if (null? pre-eval-procedures)
(read)
(let ((first-proc (car pre-eval-procedures)))
(set! pre-eval-procedures (cdr pre-eval-procedures))
first-proc)))
(define (driver-loop)
(define (internal-loop try-again)
(prompt-for-input input-prompt)
(let ((input (get-input)))
(if (eq? input 'try-again)
(try-again)
(begin
(newline)
(display ";;; Starting a new problem ")
(ambeval input
the-global-environment
;; ambeval success
(lambda (val next-alternative)
(announce-output output-prompt)
(user-print-output val)
(internal-loop next-alternative))
;; ambeval failure
(lambda ()
(announce-output
";;; There are no more values of")
(user-print-output input)
(driver-loop)))))))
(internal-loop
(lambda ()
(newline)
(display ";;; There is no current problem")
(driver-loop))))
(define (load-from-file file)
(define (loop-read port)
(let ((input (read port)))
(if (eof-object? input)
'ok
(begin (ambeval input the-global-environment
(lambda (x y) ())
(lambda () ()))
(loop-read port)))))
(loop-read (open-input-file file)))
(define primitive-procedures
(list (list 'car car)
(list 'cdr cdr)
(list 'cons cons)
(list 'null? null?)
(list 'list list)
(list 'memq memq)
(list 'member member)
(list 'not not)
(list '+ +)
(list '- -)
(list '* *)
(list '= =)
(list '> >)
(list '>= >=)
(list '<= <=)
(list 'abs abs)
(list 'remainder remainder)
(list 'integer? integer?)
(list 'sqrt sqrt)
(list 'eq? eq?)
(list 'prime? prime?) ;: load prime.scm
(list 'display display)
(list 'newline newline)
(list 'load load-from-file)
;(list 'and and)
;(list 'or or)
;(list 'read-string read-string)
;(list 'open-i/o-file open-i/o-file)
;; more primitives
))
(define pre-eval-procedures
(list '(define (require p) (if (not p) (amb)))))
(define the-global-environment (setup-environment))
(driver-loop)