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(define-module (language python for)
#:use-module (language python yield)
#:use-module (oop pf-objects)
#:use-module (language python exceptions)
#:use-module (oop goops)
#:use-module (ice-9 control)
#:export (for break next wrap-in))
(define-syntax-rule (aif it p x y) (let ((it p)) (if it x y)))
(eval-when (compile eval load)
(define (generate-temporaries2 x)
(map (lambda (x) (generate-temporaries x)) x)))
(define-syntax-parameter break (lambda (x) #f))
(define-syntax for
(syntax-rules (:)
((for ((x ... : E) ...) ((c n) ...) code ... #:final fin)
(for-work #f ((x ... : E) ...) ((c n) ...) (code ...) fin))
((for lp ((x ... : E) ...) ((c n) ...) code ... #:final fin)
(for-work lp ((x ... : E) ...) ((c n) ...) (code ...) fin))
((for ((x ... : E) ...) ((c n) ...) code ...)
(for-work #f ((x ... : E) ...) ((c n) ...) (code ...) (values)))
((for lp ((x ... : E) ...) ((c n) ...) code ...)
(for-work lp ((x ... : E) ...) ((c n) ...) (code ...) (values)))))
(define-syntax for-work
(lambda (x)
(define (wrap-continue lp code)
(if (syntax->datum lp)
#`(lambda () (let/ec #,lp #,@code))
#`(lambda () #,@code)))
(syntax-case x ()
((for lp ((x ... : E) ...) ((c n) ...) (code ...) fin)
(with-syntax (((It ...) (generate-temporaries #'(E ...)))
((cc ...) (generate-temporaries #'(c ...)))
(((x1 ...) ...) (generate-temporaries2 #'((x ...) ...)))
(((x2 ...) ...) (generate-temporaries2 #'((x ...) ...)))
(llp (if (syntax->datum #'lp) #'lp #'lpu)))
#`(let/ec lp-break
(syntax-parameterize ((break (lambda (z)
(syntax-case z ()
((_ . l)
#'(lp-break . l))
(_ #'lp-break)))))
(let ((It (wrap-in E)) ...
(c n ) ...
(x 'None ) ... ...
(x1 #f ) ... ...)
(catch StopIteration
(lambda ()
(let llp ((cc c) ...)
(set! c cc) ...
(call-with-values
(lambda () (next It))
(lambda (x2 ...)
(set! x1 x2) ...))
...
(set! x x1)
... ...
(call-with-values
#,(wrap-continue #'lp #'(code ...))
(lambda (cc ... . q) (llp cc ...)))))
(lambda q fin))))))))))
(define-class <scm-list> () l)
(define-class <scm-string> () s i)
(define-method (next (l <scm-list>))
(let ((ll (slot-ref l 'l)))
(if (pair? ll)
(begin
(slot-set! l 'l (cdr ll))
(car ll))
(throw StopIteration))))
(define-method (next (l <scm-string>))
(let ((s (slot-ref l 's))
(i (slot-ref l 'i)))
(if (= i (string-length s))
(throw StopIteration)
(begin
(slot-set! l 'i (+ i 1))
(string-ref s i)))))
(define-method (next (l <yield>))
(let ((k (slot-ref l 'k))
(s (slot-ref l 's)))
(if k
(k (lambda () 'None))
(s))))
(define-method (next (l <p>))
((ref l '__next__)))
(define-method (wrap-in (x <p>))
(aif it (ref x '__iter__ #f)
(it)
x))
(define-method (wrap-in x)
(cond
((pair? x)
(let ((o (make <scm-list>)))
(slot-set! o 'l x)
o))
((string? x)
(let ((o (make <scm-string>)))
(slot-set! o 's x)
(slot-set! o 'i 0)
o))
(else
x)))
#;
(pk
(for c ((x : (gen '(1 2 3)))) ((s 0))
(pk x)
(if (> x 2) (c s))
(+ s x)
#:final
s))
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