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def.scm
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def.scm
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;; This file is part of Scheme+
;; Copyright 2021-2024 Damien MATTEI
;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <https://www.gnu.org/licenses/>.
(define-module (def)
;;#:use-module ((guile)) ;; pourquoi (( et ))
#:use-module (srfi srfi-31) ;; rec
#:export (def return return-rec
<+ +>
⥆ ⥅
:+ +:))
;; scheme@(guile-user)> (defined-symbol? x)
;;$1 = #f
;; (define-syntax defined-symbol?
;; (syntax-rules ()
;; ((_ x) (defined? (quote x)))))
;; Warning: does not works in all context ! (limitation/bug in Guile) :
;; scheme@(guile-user)> (let () (define x 3) (defined? 'x))
;; $1 = #f ;; !!!!!!
;; scheme@(guile-user)> (defined-symbol? d)
;; ;;; <stdin>:20:17: warning: possibly unbound variable `d'
;; $3 = #f
;; (define-syntax defined-symbol?
;; (syntax-rules ()
;; ((_ x) (call-with-current-continuation
;; (lambda (exit)
;; (with-exception-handler
;; (lambda (e)
;; (display "defined-symbol? : undefined") (newline)
;; (exit #f)) ; eval failed => not defined
;; (lambda ()
;; (eval x (interaction-environment))
;; #t))))))) ; eval suceeded => defined
;; scheme@(guile-user)> (define r 2)
;; scheme@(guile-user)> (if-defined r 'defined (define r 7))
;; if-defined : where=#t
;; $16 = defined
;; scheme@(guile-user)> (if-defined t3 'defined (define t3 7))
;; if-defined : where=#f
;; scheme@(guile-user)> t3
;; $17 = 7
;; scheme@(guile-user)> (if-defined z (list z) 'not-defined)
;; if-defined : where=#f
;; $18 = not-defined
;; (define-syntax if-defined
;; (lambda (stx)
;; (syntax-case stx ()
;; ((_ id iftrue iffalse)
;; (let ((where (defined-symbol? #'id))) ;;(quote id))))
;; (display "if-defined : where=") (display where) (newline)
;; (display "id=") (display #'id) (newline)
;; (if where #'iftrue #'iffalse))))))
(define-syntax-parameter return
(lambda (stx)
(syntax-violation 'return "used outside of a def" stx)))
(define-syntax-parameter return-rec
(lambda (stx)
(syntax-violation 'return-rec "used outside of a def" stx)))
;; scheme@(guile-user)> (def (foo) (when #t (return "hello") "bye"))
;; scheme@(guile-user)> (foo)
;; "hello"
;; (def x)
;; (def (foo n)
;; (cond ((= n 0) 'end0)
;; ((= n 7) (return 'end7))
;; (else (cons n (foo {n - 1})))))
;; scheme@(guile-user)> (foo 5)
;; (5 4 3 2 1 . end0)
;; scheme@(guile-user)> (foo 10)
;; (10 9 8 . end7)
;; (def (bar n)
;; (cond ((= n 0) 'end0)
;; ((= n 7) (return-rec 'end7))
;; (else (cons n (bar {n - 1})))))
;; scheme@(guile-user)> (bar 5)
;; $4 = (5 4 3 2 1 . end0)
;; scheme@(guile-user)> (bar 10)
;; $5 = end7
(define-syntax def
(lambda (stx)
(syntax-case stx ()
;; multiple definitions without values assigned
;; (def (x y z))
((_ (var1 ...)) #`(begin (define var1 '()) ...))
;; (def (foo) (when #t (return "hello") "bye"))
;; ((_ (<name> <arg> ...) <body> <body>* ...)
;; (let ((ret-id (datum->syntax stx 'return)))
;; #`(define (<name> <arg> ...)
;; (call/cc (lambda (#,ret-id) <body> <body>* ...)))))
;; ((_ (<name> <arg> ...) <body> <body>* ...)
;; (let ((ret-id (datum->syntax stx 'return))
;; (ret-rec-id (datum->syntax stx 'return-rec)))
;; #`(define (<name> <arg> ...)
;; (call/cc (lambda (#,ret-rec-id)
;; (apply (rec <name> (lambda (<arg> ...)
;; (call/cc (lambda (#,ret-id) <body> <body>* ...)))) (list <arg> ...)))))))
((_ (<name> <arg> ...) <body> <body>* ...)
#'(define (<name> <arg> ...)
(call/cc
(lambda (ret-rec-id) ;(#,ret-rec-id)
(syntax-parameterize
([return-rec (syntax-rules ()
[(return-rec vals (... ...))
(ret-rec-id vals (... ...))])])
(apply (rec <name> (lambda (<arg> ...)
(call/cc
(lambda (ret-id) ;(#,ret-id)
;; In the body we adjust the 'return' keyword so that calls
;; to 'return' are replaced with calls to the escape
;; continuation.
(syntax-parameterize
([return (syntax-rules ()
[(return vals (... ...))
(ret-id vals (... ...))])])
<body> <body>* ...)))))
(list <arg> ...)))))))
;; single definition without a value assigned
;; (def x)
((_ var) #`(define var '()))
;; (def x 7)
((_ var expr) #`(define var expr))
((_ err ...) #`(syntax-error "Bad def form"))
)))
;; definition and assignment
;; { x <+ 7 } is equivalent to : (<- x 7) or (define x 7)
;; > {(a b c) <+ (values 7 8 9)}
;; 7
;; 8
;; 9
;; > (list a b c)
;; '(7 8 9)
;; > { y <+ z <+ 7 }
;; > z
;; 7
;; > y
;; 7
;; > { x <+ y <+ z <+ 7 }
;; > (list x y z)
;; '(7 7 7)
;; > {(x y z) <+ (u v w) <+ (a b c) <+ (values 2 4 5)}
;; 2
;; 4
;; 5
;; > (list x y z u v w a b c)
;; '(2 4 5 2 4 5 2 4 5)
(define-syntax <+
(syntax-rules ()
((_ (var1 ...) expr)
(define-values (var1 ...) expr)
)
;; (begin
;; (define var1 '())
;; ...
;; ;;(display "<+ multiple") (newline)
;; (set!-values (var1 ...) expr)))
;; > {(x y z) <+ (u v w) <+ (a b c) <+ (values 2 4 5)}
;; 2
;; 4
;; 5
;; > (list x y z u v w a b c)
;; '(2 4 5 2 4 5 2 4 5)
((_ (var10 ...) (var11 ...) ... expr) (begin ;; i do not do what the syntax says (assignation not in the good order) but it gives the same result
(define-values (var10 ...) expr)
(define-values (var11 ...) (values var10 ...))
...
))
((_ var expr) (define var expr))
;; > { y <+ z <+ 7 }
;; 7
;; > z
;; 7
;; > y
;; 7
;; > { x <+ y <+ z <+ 7 }
;; 7
;; > (list x y z)
;; '(7 7 7)
((_ var var1 ... expr) (begin ;; i do not do what the syntax says (assignation not in the good order) but it gives the same result
(define var expr)
(define var1 var)
...
;;var))
))
))
(define-syntax ⥆
(syntax-rules ()
((_ var ...) (<+ var ...))))
;; scheme@(guile-user)> {x :+ 7}
;; scheme@(guile-user)> x
;; $1 = 7
;; scheme@(guile-user)> {x := "hello"}
;; scheme@(guile-user)> x
;; $2 = "hello"
(define-syntax :+
(syntax-rules ()
((_ var ...) (<+ var ...))))
;; > {(values 2 4 5) +> (x y z) +> (u v w) +> (a b c)}
;; 2
;; 4
;; 5
(define-syntax +>
(syntax-rules ()
((_ exp var ...) (<+ var ... exp))))
(define-syntax +:
(syntax-rules ()
((_ exp var ...) (<+ var ... exp))))
;; > {(values 2 4 5) ⥅ (x y z) ⥅ (u v w) ⥅ (a b c)}
;; 2
;; 4
;; 5
;; > (list x y z u v w a b c)
;; '(2 4 5 2 4 5 2 4 5)
(define-syntax ⥅
(syntax-rules ()
((_ expr ...) (+> expr ...))))