module/system/base/language.scm

   1 ;;; Multi-language support
   2
   3 ;; Copyright (C) 2001 Free Software Foundation, Inc.
   4
   5 ;; This program is free software; you can redistribute it and/or modify
   6 ;; it under the terms of the GNU General Public License as published by
   7 ;; the Free Software Foundation; either version 2, or (at your option)
   8 ;; any later version.
   9 ;;
  10 ;; This program is distributed in the hope that it will be useful,
  11 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 ;; GNU General Public License for more details.
  14 ;;
  15 ;; You should have received a copy of the GNU General Public License
  16 ;; along with this program; see the file COPYING.  If not, write to
  17 ;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18 ;; Boston, MA 02111-1307, USA.
  19
  20 ;;; Code:
  21
  22 (define-module (system base language)
  23   #:use-module (system base syntax)
  24   #:export (define-language language? lookup-language make-language
  25             language-name language-title language-version language-reader
  26             language-printer language-parser language-read-file
  27             language-compilers language-decompilers language-evaluator
  28
  29             lookup-compilation-order lookup-decompilation-order
  30             invalidate-compilation-cache!))
  31
  32 \f
  33 ;;;
  34 ;;; Language class
  35 ;;;
  36
  37 (define-record/keywords <language>
  38   name
  39   title
  40   version
  41   reader
  42   printer
  43   (parser #f)
  44   (read-file #f)
  45   (compilers '())
  46   (decompilers '())
  47   (evaluator #f))
  48
  49 (define-macro (define-language name . spec)
  50   `(begin
  51      (invalidate-compilation-cache!)
  52      (define ,name (make-language #:name ',name ,@spec))))
  53
  54 (define (lookup-language name)
  55   (let ((m (resolve-module `(language ,name spec))))
  56     (if (module-bound? m name)
  57         (module-ref m name)
  58         (error "no such language" name))))
  59
  60 (define *compilation-cache* '())
  61 (define *decompilation-cache* '())
  62
  63 (define (invalidate-compilation-cache!)
  64   (set! *decompilation-cache* '())
  65   (set! *compilation-cache* '()))
  66
  67 (define (compute-translation-order from to language-translators)
  68   (cond
  69    ((not (language? to))
  70     (compute-translation-order from (lookup-language to) language-translators))
  71    (else
  72     (let lp ((from from) (seen '()))
  73       (cond
  74        ((not (language? from))
  75         (lp (lookup-language from) seen))
  76        ((eq? from to) (reverse! seen))
  77        ((memq from seen) #f)
  78        (else (or-map (lambda (pair)
  79                        (lp (car pair) (acons from (cdr pair) seen)))
  80                      (language-translators from))))))))
  81
  82 (define (lookup-compilation-order from to)
  83   (let ((key (cons from to)))
  84     (or (assoc-ref *compilation-cache* key)
  85         (let ((order (compute-translation-order from to language-compilers)))
  86           (set! *compilation-cache*
  87                 (acons key order *compilation-cache*))
  88           order))))
  89
  90 (define (lookup-decompilation-order from to)
  91   (let ((key (cons from to)))
  92     (or (assoc-ref *decompilation-cache* key)
  93         ;; trickery!
  94         (let ((order (and=>
  95                       (compute-translation-order to from language-decompilers)
  96                       reverse!)))
  97           (set! *decompilation-cache* (acons key order *decompilation-cache*))
  98           order))))