define-syntax...
This commit is contained in:
Jan Nieuwenhuizen
parent
d53ea79a5d
commit
21a5e16a88
397
syntax.mes
397
syntax.mes
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@ -1,22 +1,100 @@
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(define else #t)
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(define (syntax-error message thing)
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(display "syntax-error:")
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(display message)
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(display ":")
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;;(display thing)
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(newline))
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(display "define-syntax...")
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(define-macro define-syntax
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(lambda (form expander)
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(expander `(define-macro ,(cadr form)
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(let ((transformer ,(caddr form)))
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(lambda (form expander)
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(expander (transformer form
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(lambda (x) x)
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eq?)
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expander))))
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expander)))
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;;(define (caddr x) (car (cdr (cdr x))))
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;; (define (caddr x)
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;; (display "wanna caddr:")
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;; (display x)
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;; (newline))
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;; (define-macro define-syntax
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;; (lambda (form expander)
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;; (expander `(define-macro ,(cadr form)
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;; (let ((transformer ,(caddr form)))
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;; (lambda (form expander)
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;; (expander (transformer form
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;; (lambda (x) x)
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;; eq?)
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;; expander))))
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;; expander)))
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;; (define (dinges form expander)
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;; (display "dinges form:")
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;; (display form)
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;; (newline)
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;; `(define-macro BOO ;;;,(cadr form)
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;; (let ((transformer ,(caddr form)))
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;; (lambda (form expander)
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;; (expander (transformer form
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;; (lambda (x) x)
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;; eq?)
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;; expander)))))
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;; (define-macro (define-syntax form expander)
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;; `(expander (dinges form expander)
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;; expander))
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(define-macro (define-syntax macro-name transformer . stuff)
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;; (display "define-syntax:")
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;; (newline)
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;; (display `(define-macro (,macro-name . args)
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;; (,transformer (cons ',macro-name args)
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;; (lambda (x) x)
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;; eq?)))
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;; (newline)
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`(define-macro (,macro-name . args)
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(
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,transformer (cons ',macro-name args)
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(lambda (x) x)
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eq?
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)
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)
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)
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;; (define-macro (define-syntax form expander)
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;; (expander `(define-macro ,(cadr form)
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;; (let ((transformer ,(caddr form)))
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;; (lambda (form expander)
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;; (expander (transformer form
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;; (lambda (x) x)
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;; eq?)
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;; expander))))
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;; expander))
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;; (define-macro (define-syntax form expander)
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;; (expander `(define-macro ((cadr form) form expander)
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;; (let ((transformer (caddr form)))
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;; (expander (transformer form
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;; (lambda (x) x)
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;; eq?)
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;; expander)))
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;; expander))
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(newline)
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(display "define-syntax when...")
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(display "define-syntax syntax-rules...")
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(newline)
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;; (define-macro (syntax-rules exp r c))
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;; (define-syntax syntax-rules
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;; (let ()
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;; (lambda (exp r c)
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;; (display "hallo")
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;; (display "newline"))))
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;; (define-syntax syntax-rules
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;; (lambda (exp r c)
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;; (display "hallo")
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;; (display "newline")))
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(define-syntax syntax-rules
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(let ()
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@ -25,16 +103,16 @@
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(define (segment-pattern? pattern)
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(and (segment-template? pattern)
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(or (null? (cddr pattern))
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(syntax-error "segment matching not implemented" pattern))))
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(or (null? (cddr pattern))
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(syntax-error "segment matching not implemented" pattern))))
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(define (segment-template? pattern)
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(and (pair? pattern)
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(pair? (cdr pattern))
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(memq (cadr pattern) indicators-for-zero-or-more)))
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(pair? (cdr pattern))
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(memq (cadr pattern) indicators-for-zero-or-more)))
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(define indicators-for-zero-or-more (list (string->symbol "...") '---))
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(lambda (exp r c)
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(define %input (r '%input)) ;Gensym these, if you like.
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@ -46,163 +124,179 @@
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(define rules (cddr exp))
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(define subkeywords (cadr exp))
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(define (make-transformer rules)
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`(lambda (,%input ,%rename ,%compare)
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(let ((,%tail (cdr ,%input)))
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(cond ,@(map process-rule rules)
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(else
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(syntax-error
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"use of macro doesn't match definition"
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,%input))))))
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(define (make-transformer rules)
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`(lambda (,%input ,%rename ,%compare)
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(let ((,%tail (cdr ,%input)))
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(cond ,@(map process-rule rules)
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(else
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(syntax-error
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"use of macro doesn't match definition"
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,%input))))))
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(define (process-rule rule)
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(if (and (pair? rule)
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(pair? (cdr rule))
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(null? (cddr rule)))
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(let ((pattern (cdar rule))
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(template (cadr rule)))
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`((and ,@(process-match %tail pattern))
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(let* ,(process-pattern pattern
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%tail
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(lambda (x) x))
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,(process-template template
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0
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(meta-variables pattern 0 '())))))
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(syntax-error "ill-formed syntax rule" rule)))
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(define (process-rule rule)
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(if (and (pair? rule)
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(pair? (cdr rule))
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(null? (cddr rule)))
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(let ((pattern (cdar rule))
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(template (cadr rule)))
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`((and ,@(process-match %tail pattern))
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(let* ,(process-pattern pattern
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%tail
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(lambda (x) x))
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,(process-template template
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0
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(meta-variables pattern 0 '())))))
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(syntax-error "ill-formed syntax rule" rule)))
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; Generate code to test whether input expression matches pattern
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;; Generate code to test whether input expression matches pattern
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(define (process-match input pattern)
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(cond ((name? pattern)
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(if (member pattern subkeywords)
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`((,%compare ,input (,%rename ',pattern)))
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`()))
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((segment-pattern? pattern)
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(process-segment-match input (car pattern)))
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((pair? pattern)
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`((let ((,%temp ,input))
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(and (pair? ,%temp)
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,@(process-match `(car ,%temp) (car pattern))
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,@(process-match `(cdr ,%temp) (cdr pattern))))))
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((or (null? pattern) (boolean? pattern) (char? pattern))
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`((eq? ,input ',pattern)))
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(else
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`((equal? ,input ',pattern)))))
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(define (process-match input pattern)
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(cond ((name? pattern)
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(if (member pattern subkeywords)
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`((,%compare ,input (,%rename ',pattern)))
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`()))
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((segment-pattern? pattern)
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(process-segment-match input (car pattern)))
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((pair? pattern)
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`((let ((,%temp ,input))
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(and (pair? ,%temp)
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,@(process-match `(car ,%temp) (car pattern))
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,@(process-match `(cdr ,%temp) (cdr pattern))))))
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((or (null? pattern) (boolean? pattern) (char? pattern))
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`((eq? ,input ',pattern)))
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(else
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`((equal? ,input ',pattern)))))
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(define (process-segment-match input pattern)
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(let ((conjuncts (process-match '(car l) pattern)))
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(if (null? conjuncts)
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`((list? ,input)) ;+++
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`((let loop ((l ,input))
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(or (null? l)
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(and (pair? l)
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,@conjuncts
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(loop (cdr l)))))))))
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(define (process-segment-match input pattern)
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(let ((conjuncts (process-match '(car l) pattern)))
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(if (null? conjuncts)
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`((list? ,input)) ;+++
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`((let loop ((l ,input))
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(or (null? l)
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(and (pair? l)
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,@conjuncts
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(loop (cdr l)))))))))
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; Generate code to take apart the input expression
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; This is pretty bad, but it seems to work (can't say why).
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;; Generate code to take apart the input expression
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;; This is pretty bad, but it seems to work (can't say why).
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(define (process-pattern pattern path mapit)
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(cond ((name? pattern)
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(if (memq pattern subkeywords)
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'()
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(list (list pattern (mapit path)))))
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((segment-pattern? pattern)
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(process-pattern (car pattern)
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%temp
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(lambda (x) ;temp is free in x
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(mapit (if (eq? %temp x)
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path ;+++
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`(map (lambda (,%temp) ,x)
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,path))))))
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((pair? pattern)
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(append (process-pattern (car pattern) `(car ,path) mapit)
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(process-pattern (cdr pattern) `(cdr ,path) mapit)))
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(else '())))
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(define (process-pattern pattern path mapit)
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(cond ((name? pattern)
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(if (memq pattern subkeywords)
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'()
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(list (list pattern (mapit path)))))
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((segment-pattern? pattern)
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(process-pattern (car pattern)
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%temp
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(lambda (x) ;temp is free in x
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(mapit (if (eq? %temp x)
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path ;+++
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`(map (lambda (,%temp) ,x)
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,path))))))
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((pair? pattern)
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(append (process-pattern (car pattern) `(car ,path) mapit)
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(process-pattern (cdr pattern) `(cdr ,path) mapit)))
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(else '())))
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; Generate code to compose the output expression according to template
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;; Generate code to compose the output expression according to template
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(define (process-template template rank env)
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(cond ((name? template)
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(let ((probe (assq template env)))
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(if probe
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(if (<= (cdr probe) rank)
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template
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(syntax-error "template rank error (too few ...'s?)"
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template))
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`(,%rename ',template))))
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((segment-template? template)
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(let ((vars
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(free-meta-variables (car template) (+ rank 1) env '())))
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(if (null? vars)
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(syntax-error "too many ...'s" template)
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(let* ((x (process-template (car template)
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(+ rank 1)
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env))
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(gen (if (equal? (list x) vars)
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x ;+++
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`(map (lambda ,vars ,x)
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,@vars))))
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(if (null? (cddr template))
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gen ;+++
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`(append ,gen ,(process-template (cddr template)
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rank env)))))))
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((pair? template)
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`(cons ,(process-template (car template) rank env)
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,(process-template (cdr template) rank env)))
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(else `(quote ,template))))
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(define (process-template template rank env)
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(cond ((name? template)
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(let ((probe (assq template env)))
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(if probe
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(if (<= (cdr probe) rank)
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template
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(syntax-error "template rank error (too few ...'s?)"
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template))
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`(,%rename ',template))))
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((segment-template? template)
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(let ((vars
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(free-meta-variables (car template) (+ rank 1) env '())))
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(if (null? vars)
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(syntax-error "too many ...'s" template)
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(let* ((x (process-template (car template)
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(+ rank 1)
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env))
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(gen (if (equal? (list x) vars)
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x ;+++
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`(map (lambda ,vars ,x)
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,@vars))))
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(if (null? (cddr template))
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gen ;+++
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`(append ,gen ,(process-template (cddr template)
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rank env)))))))
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((pair? template)
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`(cons ,(process-template (car template) rank env)
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,(process-template (cdr template) rank env)))
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(else `(quote ,template))))
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; Return an association list of (var . rank)
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; Return an association list of (var . rank)
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(define (meta-variables pattern rank vars)
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(cond ((name? pattern)
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(if (memq pattern subkeywords)
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vars
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(cons (cons pattern rank) vars)))
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((segment-pattern? pattern)
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(meta-variables (car pattern) (+ rank 1) vars))
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((pair? pattern)
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(meta-variables (car pattern) rank
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(meta-variables (cdr pattern) rank vars)))
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(else vars)))
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(define (meta-variables pattern rank vars)
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(cond ((name? pattern)
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(if (memq pattern subkeywords)
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vars
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(cons (cons pattern rank) vars)))
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((segment-pattern? pattern)
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(meta-variables (car pattern) (+ rank 1) vars))
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((pair? pattern)
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(meta-variables (car pattern) rank
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(meta-variables (cdr pattern) rank vars)))
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(else vars)))
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; Return a list of meta-variables of given higher rank
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; Return a list of meta-variables of given higher rank
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(define (free-meta-variables template rank env free)
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(cond ((name? template)
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(if (and (not (memq template free))
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(let ((probe (assq template env)))
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(and probe (>= (cdr probe) rank))))
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(cons template free)
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free))
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((segment-template? template)
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(free-meta-variables (car template)
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rank env
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(free-meta-variables (cddr template)
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rank env free)))
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((pair? template)
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(free-meta-variables (car template)
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rank env
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(free-meta-variables (cdr template)
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rank env free)))
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(else free)))
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(define (free-meta-variables template rank env free)
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(cond ((name? template)
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(if (and (not (memq template free))
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(let ((probe (assq template env)))
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(and probe (>= (cdr probe) rank))))
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(cons template free)
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free))
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((segment-template? template)
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(free-meta-variables (car template)
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rank env
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(free-meta-variables (cddr template)
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rank env free)))
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((pair? template)
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(free-meta-variables (car template)
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rank env
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(free-meta-variables (cdr template)
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rank env free)))
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(else free)))
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c ;ignored
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;;c ;ignored
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;; Kludge for Scheme48 linker.
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;; `(cons ,(make-transformer rules)
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;; ',(find-free-names-in-syntax-rules subkeywords rules))
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;; Kludge for Scheme48 linker.
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;; `(cons ,(make-transformer rules)
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;; ',(find-free-names-in-syntax-rules subkeywords rules))
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(make-transformer rules))))
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(make-transformer rules))))
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;; (define-syntax or
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;; (syntax-rules ()
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;; ((or) #f)
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;; ((or e) e)
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;; ((or e1 e ...) (let ((temp e1))
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;; (if temp temp (or e ...))))))
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;; (define-syntax when
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;; (define-syntax xwhen
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;; (syntax-rules ()
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;; ((when condition exp ...)
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;; (if condition
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;; (begin exp ...)))))
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;; (display "define-when: ")
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;; (display
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;; (define-syntax xwhen
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;; (syntax-rules ()
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;; ((when condition exp ...)
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;; (if condition
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;; (begin exp ...))))))
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;; (newline)
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;; (display (xwhen #t "hello syntax world"))
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;; (define-macro (when cond exp . rest)
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;; `(if ,cond
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;; (begin ,exp . ,rest)))
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@ -211,3 +305,6 @@
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;; (define-macro (when clause . rest)
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;; (list 'cond (list clause (list 'let '() rest))))
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(newline)
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'boo
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EOF
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'()
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