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preprocess.ss
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155 lines (145 loc) · 6.24 KB
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(define *stx* (make-eq-hashtable))
(define *void* (void))
(define (*id* x) x)
(define-syntax assert
(syntax-rules ()
[(_ x) (unless x
(error 'assert "Assertion failed" 'x))]))
(define-syntax debug
(syntax-rules ()
[(_ ...) (void)]
[(_) (void)]
[(_ x) (begin
(display "***")
(pretty-print 'x)
(pretty-print x))]
[(_ x y ...) (begin (debug x) (debug y ...))]))
(define-syntax debug1
(syntax-rules ()
[(_) (void)]
[(_ x) (begin
(display "***")
(pretty-print 'x)
(pretty-print x))]
[(_ x y ...) (begin (debug1 x) (debug1 y ...))]))
(define (preprocess lst)
(define (analyze ls pat? sp?)
; 'p => pair
; ... => block ...
; #t/#f => (sp? atom)
(if (pair? ls)
(let ([x (analyze (car ls) pat? sp?)] [ls (cdr ls)])
(if (and (pair? ls) (eq? (car ls) '...))
(if pat? `(... . ,x)
(cons* 'p `(... . ,x) (analyze (cdr ls) #f sp?)))
(cons* 'p x (analyze ls pat? sp?))))
(if (null? ls) ls
(cons (sp? ls) ls))))
(define (process-pattern keywords)
(lambda (entry)
(define var '())
(define pattern
(analyze (cdar entry) #t
(lambda (x)
(or (not (symbol? x))
(and (memq x keywords) #t)
(begin (set! var (cons x var)) #f)))))
(define output
(analyze (cdr entry) #f
(lambda (x) (and (memq x var) #t))))
(cons pattern output)))
(define (pattern-match stx ls)
(define-record-type ellipsis (fields data))
(define (ellipsis->string x)
(cond
[(pair? x) (cons (ellipsis->string (car x))
(ellipsis->string (cdr x)))]
[(ellipsis? x) (assert (list? (ellipsis-data x)))
(cons '... (ellipsis->string (ellipsis-data x)))]
[else x]))
(define (print-ellipsis x) (pretty-print (ellipsis->string x)))
(define var
(let match ([pat (car stx)] [ls ls])
(if (null? pat) (and (null? ls) ls)
(let ([t (car pat)] [pat (cdr pat)])
(case t
[(p) (let ([ma (match (car pat) (car ls))])
(and ma (let ([md (match (cdr pat) (cdr ls))])
(and md (append ma md)))))]
[(...) (and (list? ls)
(if (and (null? ls) (not (car pat)))
(list (cons (cdr pat) (make-ellipsis ls)))
(let loop ([ls (reverse ls)] [var '()])
(if (null? ls)
(map (lambda (e) (cons (car e) (make-ellipsis (cdr e)))) var)
(let ([x (match pat (car ls))])
(and x (loop (cdr ls)
(if (null? var)
(map (lambda (e) (list (car e) (cdr e))) x)
(map (lambda (e1 e2)
(define name (car e1))
(assert (eq? name (car e2)))
(let* ([v1 (cdr e1)] [v2 (cdr e2)] [v (car v1)])
(cons* name v2
(if (not (ellipsis? v)) v1
(begin
(assert (ellipsis? v2))
(cons (ellipsis-data v) (cdr v1)))))))
var x)))))))))]
[(#t) (and (eq? pat ls) '())]
[(#f) `((,pat . ,ls))])))))
(and var
(let output ([out (cdr stx)])
(if (null? out) out
(let ([t (car out)] [out (cdr out)])
(case t
[(p) (let ([a (car out)] [d (cdr out)])
(let ([oa (output a)] [od (output d)])
((if (and (pair? a) (eq? (car a) '...)) append
cons) oa od)))]
[(...) (let loop ([x (output out)] [out '()])
(let ([has-car? #f] [has-null? #f] [ls '()] [x* #f])
(if (pair? x)
(let loop ([x x] [x** #f])
#f
)
(let ([x (ellipsis-data x)])
(if (null? x) (set! has-null? #t)
(begin
(set! has-car? #t)
(set! ls (car x))
(set! x* (make-ellipsis (cdr x)))))))
(if has-null?
(if (not has-car?) (reverse! out)
(error 'expand-syntax "wrong length"))
(if has-car? (loop x* (cons ls out))
(if (null? out) out
(error 'expand-syntax "all constant"))))))]
[(#t) (cdr (assq out var))]
[(#f) out]))))))
(if (not (pair? lst)) lst
(let ([h (car lst)] [ls (cdr lst)])
(case h
[(quote) lst]
[(define-syntax)
(let ([name (car ls)] [ls (cdr ls)])
(hashtable-set! *stx* name
(map (process-pattern (car ls)) (cdr ls))))]
[else (let ([stx (hashtable-ref *stx* h #f)])
(if stx
(let loop ([stx stx])
(cond
[(null? stx) (error 'expand-macro "Invaild syntax" lst)]
[(pattern-match (car stx) ls) => car]
[else (loop (cdr stx))]))
(cons (preprocess h) (preprocess ls))))]))))
(let loop ()
(let process ([ls (read)])
(let ([lst (preprocess ls)])
(if (equal? lst ls)
(unless (eof-object? ls)
(unless (eq? ls *void*)
(write ls)
(newline))
(loop))
(process lst)))))