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def.rkt
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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/>.
(module def racket/base
(provide def return return-rec
<+ +>
⥆ ⥅
:+ +:
if-defined)
(require srfi/31 ;; for 'rec in def.scm
racket/stxparam
(for-syntax racket/base))
; Tests
;; (define x 3)
;; (if (defined? x) 'defined 'not-defined) ; -> defined
;; (let ([y 4])
;; (if (defined? y) 'defined 'not-defined)) ; -> defined
;; (if (defined? z) 'defined 'not-defined) ; -> not-defined
;; (define-syntax (defined? stx)
;; (syntax-case stx ()
;; [(_ id)
;; (with-syntax ([v (identifier-binding #'id)]) ; Racket feature , not RnRS
;; #''v)]))
; Tests
;; (if-defined z (list z) 'not-defined) ; -> not-defined
;; (if-defined t (void) (define t 5))
;; t ; -> 5
;; (define x 3)
;; (if-defined x (void) (define x 6))
;; x ; -> 3
;;(define-syntax (if-defined stx)
(define-syntax if-defined
(lambda (stx)
(syntax-case stx ()
[(_ id iftrue iffalse)
(let ([exist-id (identifier-binding #'id)])
;;(display "id=") (display #'id) (newline)
;;(display "if-defined : exist-id=") (display exist-id) (newline) (newline)
(if exist-id #'iftrue #'iffalse))])))
(define-syntax-parameter return-rec
(lambda (stx)
(raise-syntax-error 'return-rec "can only be used inside def")))
(define-syntax-parameter return
(lambda (stx)
(raise-syntax-error 'return "can only be used inside def")))
;; Welcome to DrRacket, version 8.14 [cs].
;; Language: racket, with debugging; memory limit: 8192 MB.
;; > (require Scheme+/def)
;; > (def (foo) (display "hello") (newline) (return) (display "world") (newline))
;; > (foo)
;; hello
;; > (return)
;; return: can only be used inside def
;; scheme@(guile-user)> (def (foo) (when #t (return "hello") "bye"))
;; scheme@(guile-user)> (foo)
;; "hello"
;; (def x)
;;(define return '()) ;; for debug of Typed Racket
(define-syntax def
(lambda (stx)
(syntax-case stx ()
;; multiple definitions without values assigned
;; (def (x y z))
;; TODO: remove? redundant with (declare 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>* ...)
;; (with-syntax ((ret-id (datum->syntax stx 'return))
;; (ret-rec-id (datum->syntax stx 'return-rec)))
;; (display "def.scm : def : ret-id = ") (display #'ret-id) (newline)
;; (display "def.scm : def : ret-rec-id = ") (display #'ret-rec-id) (newline)
;; #'(define (<name> <arg> ...)
;; (call/cc (lambda (ret-rec-id) ;(#,ret-rec-id)
;; (apply (rec <name> (lambda (<arg> ...)
;; (call/cc
;; (lambda (ret-id) ;(#,ret-id)
;; <body> <body>* ...))))
;; (list <arg> ...)))))))
((_ (<name> <arg> ...) <body> <body>* ...)
#'(define (<name> <arg> ...)
(call/cc
(lambda (ret-rec-id) ;(#,ret-rec-id)
;; In the body we adjust the 'return-rec' keyword so that calls
;; to 'return-rec' are replaced with calls to the escape
;; continuation.
(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)
;; to define vector based on another vector slice:
;; {T0 <+ #(1 2 3 4 5 6 7 8 9)}
;; '#(1 2 3 4 5 6 7 8 9)
;; > '{T <+ {T0[3 / 5]}}
;; '(<+ T ($bracket-apply$ T0 3 / 5))
;; > {T <+ {T0[3 / 5]}}
;; '#(4 5)
;; > T0
;; '#(1 2 3 4 5 6 7 8 9)
;; > T
;; '#(4 5)
(define-syntax <+
(syntax-rules ()
((_ (var1 ...) expr) ;;(begin
(define-values (var1 ...) expr)
)
;;)
;;(values var1 ...)))
;; (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 ...))
...
))
;;(values var10 ...)))
((_ var expr)
;; (begin
;; (define var expr)
;; var))
(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 ...))))
(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 ...))))
(define-syntax ⥅
(syntax-rules ()
((_ exp var ...) (<+ var ... exp))))
) ; end library