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|
; -*- Mode: Scheme; Syntax: Scheme; Package: Scheme; -*-
; Part of Scheme 48 1.9. See file COPYING for notices and license.
; Authors: Richard Kelsey, Jonathan Rees, Mike Sperber
; This is file write.scm.
;;;; WRITE
; To use this with some Scheme other than Scheme 48, do the following:
; 1. Copy the definition of output-port-option from port.scm
; 2. Define write-string as appropriate (as a write-char loop)
; 3. (define (disclose x) #f)
(define (write obj . port-option)
(let ((port (output-port-option port-option)))
(if (and (output-port? port)
(open-output-port? port))
(let recur ((obj obj))
(recurring-write obj port recur))
(assertion-violation 'write "invalid port argument" port))))
(define (recurring-write obj port recur)
(cond ((null? obj) (write-string "()" port))
((pair? obj) (write-list obj port recur))
((eq? obj #t) (write-boolean 't port))
((eq? obj #f) (write-boolean 'f port))
((symbol? obj) (write-string (symbol->string obj) port))
((number? obj) (write-number obj port))
((string? obj) (write-string-literal obj port))
((char? obj) (write-char-literal obj port))
(else (write-other obj port recur))))
(define (write-boolean mumble port)
(write-char #\# port)
(write mumble port))
(define (write-number n port)
(write-string (number->string n 10) port))
(define (write-char-literal obj port)
(let ((probe (character-name obj)))
(write-string "#\\" port)
(if probe
(write probe port)
(write-char obj port))))
; These are from Matthew Flatt's Unicode proposal for R6RS
; See read.scm.
; Don't use non-R5RS char literals to avoid bootstrap circularities
(define *nul* (scalar-value->char 0))
(define *alarm* (scalar-value->char 7))
(define *backspace* (scalar-value->char 8))
(define *tab* (scalar-value->char 9))
(define *linefeed* (scalar-value->char 10))
(define *vtab* (scalar-value->char 11))
(define *page* (scalar-value->char 12))
(define *return* (scalar-value->char 13))
(define *escape* (scalar-value->char 27))
(define *rubout* (scalar-value->char 127))
(define *char-name-table*
(list
(cons #\space 'space)
(cons #\newline 'newline)
(cons *nul* 'nul)
(cons *alarm* 'alarm)
(cons *backspace* 'backspace)
(cons *tab* 'tab)
(cons *linefeed* 'linefeed)
(cons *vtab* 'vtab)
(cons *page* 'page)
(cons *return* 'return)
(cons *escape* 'escape)
(cons *rubout* 'rubout)))
(define (character-name char)
(cond ((assq char *char-name-table*)
=> cdr)
(else #f)))
(define (write-string-literal obj port)
(write-char #\" port)
(let ((len (string-length obj)))
(do ((i 0 (+ i 1)))
((= i len) (write-char #\" port))
(let ((c (string-ref obj i)))
(cond
((or (char=? c #\\) (char=? c #\"))
(write-char #\\ port)
(write-char c port))
((char=? c *alarm*) (write-string "\\a" port))
((char=? c *backspace*) (write-string "\\b" port))
((char=? c *tab*) (write-string "\\t" port))
((char=? c *linefeed*) (write-string "\\n" port))
((char=? c *vtab*) (write-string "\\v" port))
((char=? c *page*) (write-string "\\f" port))
((char=? c *return*) (write-string "\\r" port))
((char=? c *escape*) (write-string "\\e" port))
(else
(write-char c port)))))))
(define (write-list obj port recur)
(cond ((quotation? obj)
(write-char #\' port)
(recur (cadr obj)))
(else
(write-char #\( port)
(recur (car obj))
(let loop ((l (cdr obj))
(n 1))
(cond ((not (pair? l))
(cond ((not (null? l))
(write-string " . " port)
(recur l))))
(else
(write-char #\space port)
(recur (car l))
(loop (cdr l) (+ n 1)))))
(write-char #\) port))))
(define (quotation? obj)
(and (pair? obj)
(eq? (car obj) 'quote)
(pair? (cdr obj))
(null? (cddr obj))))
(define (write-vector obj port recur)
(write-string "#(" port)
(let ((z (vector-length obj)))
(cond ((> z 0)
(recur (vector-ref obj 0))
(let loop ((i 1))
(cond ((>= i z))
(else
(write-char #\space port)
(recur (vector-ref obj i))
(loop (+ i 1))))))))
(write-char #\) port))
; The vector case goes last just so that this version of WRITE can be
; used in Scheme implementations in which records, ports, or
; procedures are represented as vectors. (Scheme 48 doesn't have this
; property.)
(define (write-other obj port recur)
(cond ((disclose obj)
=> (lambda (l)
(write-string "#{" port)
(display (car l) port)
(for-each (lambda (x)
(write-char #\space port)
(recur x))
(cdr l))
(write-string "}" port)))
((eof-object? obj) (write-string "#{End-of-file}" port))
((vector? obj) (write-vector obj port recur))
((procedure? obj) (write-string "#{Procedure}" port))
((code-vector? obj)
(write-string "#{Byte-vector}" port))
((channel? obj)
(write-string "#{Channel " port)
(display (channel-id obj) port)
(write-string "}" port))
((eq? obj (if #f #f)) (write-string "#{Unspecific}" port))
(else
(write-string "#{Random object}" port))))
;(define (write-string s port)
; (do ((i 0 (+ i 1)))
; ((= i (string-length s)))
; (write-char (string-ref s i) port)))
; DISPLAY
(define (display obj . port-option)
(let ((port (output-port-option port-option)))
(if (and (output-port? port)
(open-output-port? port))
(let recur ((obj obj))
(cond ((string? obj) (write-string obj port))
((char? obj) (write-char obj port))
(else
(recurring-write obj port recur))))
(assertion-violation 'display "invalid port argument" port))))
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