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Add support for R6RS/SRFI-30 nested block comments.

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Suggested by Andreas Rottmann <a.rottmann@gmx.at>.

* libguile/read.c (flush_ws, scm_read_sharp): Add support for
  R6RS/SRFI-30 block comments.
  (scm_read_r6rs_block_comment): New function.

* test-suite/tests/reader.test (exception:unterminated-block-comment):
  Adjust to match both block comment styles.
  ("reading")["R6RS/SRFI-30 block comment", "R6RS/SRFI-30 nested block
  comment", "R6RS/SRFI-30 block comment syntax overridden"]: New tests.
  ("exceptions")["R6RS/SRFI-30 unterminated nested block comment"]: New
  test.

* doc/ref/api-evaluation.texi (Block Comments): Mention SRFI-30/R6RS
  block comments.

* doc/ref/srfi-modules.texi (SRFI-30): New node.
This commit is contained in:
Ludovic Courtès 2009-10-19 22:38:34 +02:00
parent cbeb479c6e
commit 620c89651a
4 changed files with 117 additions and 8 deletions
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15
doc/ref/api-evaluation.texi
View file

@ -230,6 +230,21 @@ Thus a Guile script often starts like this.
More details on Guile scripting can be found in the scripting section
(@pxref{Guile Scripting}).
@cindex R6RS block comments
@cindex SRFI-30 block comments
Similarly, Guile (starting from version 2.0) supports nested block
comments as specified by R6RS and
@url{http://srfi.schemers.org/srfi-30/srfi-30.html, SRFI-30}:
@lisp
(+ #| this is a #| nested |# block comment |# 2)
@result{} 3
@end lisp
For backward compatibility, this syntax can be overridden with
@code{read-hash-extend} (@pxref{Reader Extensions,
@code{read-hash-extend}}).
There is one special case where the contents of a comment can actually
affect the interpretation of code. When a character encoding
declaration, such as @code{coding: utf-8} appears in one of the first

10
doc/ref/srfi-modules.texi
View file

@ -1,6 +1,6 @@
@c -*-texinfo-*-
@c This is part of the GNU Guile Reference Manual.
@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008
@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008, 2009
@c Free Software Foundation, Inc.
@c See the file guile.texi for copying conditions.
@ -37,6 +37,7 @@ get the relevant SRFI documents from the SRFI home page
* SRFI-18:: Multithreading support
* SRFI-19:: Time/Date library.
* SRFI-26:: Specializing parameters
* SRFI-30:: Nested multi-line block comments
* SRFI-31:: A special form `rec' for recursive evaluation
* SRFI-34:: Exception handling.
* SRFI-35:: Conditions.
@ -2712,6 +2713,13 @@ or similar is typical.
@end example
@end deffn
@node SRFI-30
@subsection SRFI-30 - Nested Multi-line Comments
@cindex SRFI-30
Starting from version 2.0, Guile's @code{read} supports SRFI-30/R6RS
nested multi-line comments by default, @ref{Block Comments}.
@node SRFI-31
@subsection SRFI-31 - A special form `rec' for recursive evaluation
@cindex SRFI-31

68
libguile/read.c
View file

@ -181,8 +181,10 @@ static SCM *scm_read_hash_procedures;
|| ((_chr) == 'd') || ((_chr) == 'l'))
/* Read an SCSH block comment. */
static inline SCM scm_read_scsh_block_comment (int chr, SCM port);
static SCM scm_read_commented_expression (int chr, SCM port);
static inline SCM scm_read_scsh_block_comment (scm_t_wchar, SCM);
static SCM scm_read_r6rs_block_comment (scm_t_wchar, SCM);
static SCM scm_read_commented_expression (scm_t_wchar, SCM);
static SCM scm_get_hash_procedure (int);
/* Read from PORT until a delimiter (e.g., a whitespace) is read. Return
zero if the whole token fits in BUF, non-zero otherwise. */
@ -289,6 +291,13 @@ flush_ws (SCM port, const char *eoferr)
case ';':
scm_read_commented_expression (c, port);
break;
case '|':
if (scm_is_false (scm_get_hash_procedure (c)))
{
scm_read_r6rs_block_comment (c, port);
break;
}
/* fall through */
default:
scm_ungetc (c, port);
return '#';
@ -313,7 +322,6 @@ flush_ws (SCM port, const char *eoferr)
static SCM scm_read_expression (SCM port);
static SCM scm_read_sharp (int chr, SCM port);
static SCM scm_get_hash_procedure (int c);
static SCM recsexpr (SCM obj, long line, int column, SCM filename);
@ -990,6 +998,45 @@ scm_read_scsh_block_comment (scm_t_wchar chr, SCM port)
return SCM_UNSPECIFIED;
}
static SCM
scm_read_r6rs_block_comment (scm_t_wchar chr, SCM port)
{
/* Unlike SCSH-style block comments, SRFI-30/R6RS block comments may be
nested. So care must be taken. */
int nesting_level = 1;
int opening_seen = 0, closing_seen = 0;
while (nesting_level > 0)
{
int c = scm_getc (port);
if (c == EOF)
scm_i_input_error (__FUNCTION__, port,
"unterminated `#| ... |#' comment", SCM_EOL);
if (opening_seen)
{
if (c == '|')
nesting_level++;
opening_seen = 0;
}
else if (closing_seen)
{
if (c == '#')
nesting_level--;
closing_seen = 0;
}
else if (c == '|')
closing_seen = 1;
else if (c == '#')
opening_seen = 1;
else
opening_seen = closing_seen = 0;
}
return SCM_UNSPECIFIED;
}
static SCM
scm_read_commented_expression (scm_t_wchar chr, SCM port)
{
@ -1173,8 +1220,19 @@ scm_read_sharp (scm_t_wchar chr, SCM port)
default:
result = scm_read_sharp_extension (chr, port);
if (scm_is_eq (result, SCM_UNSPECIFIED))
scm_i_input_error (FUNC_NAME, port, "Unknown # object: ~S",
scm_list_1 (SCM_MAKE_CHAR (chr)));
{
/* To remain compatible with 1.8 and earlier, the following
characters have lower precedence than `read-hash-extend'
characters. */
switch (chr)
{
case '|':
return scm_read_r6rs_block_comment (chr, port);
default:
scm_i_input_error (FUNC_NAME, port, "Unknown # object: ~S",
scm_list_1 (SCM_MAKE_CHAR (chr)));
}
}
else
return result;
}

32
test-suite/tests/reader.test
View file

@ -1,6 +1,6 @@
;;;; reader.test --- Exercise the reader. -*- Scheme -*-
;;;;
;;;; Copyright (C) 1999, 2001, 2002, 2003, 2007, 2008 Free Software Foundation, Inc.
;;;; Copyright (C) 1999, 2001, 2002, 2003, 2007, 2008, 2009 Free Software Foundation, Inc.
;;;; Jim Blandy <jimb@red-bean.com>
;;;;
;;;; This library is free software; you can redistribute it and/or
@ -18,6 +18,7 @@
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
(define-module (test-suite reader)
:use-module (srfi srfi-1)
:use-module (test-suite lib))
@ -26,7 +27,7 @@
(define exception:unexpected-rparen
(cons 'read-error "unexpected \")\"$"))
(define exception:unterminated-block-comment
(cons 'read-error "unterminated `#! ... !#' comment$"))
(cons 'read-error "unterminated `#. \\.\\.\\. .#' comment$"))
(define exception:unknown-character-name
(cons 'read-error "unknown character name .*$"))
(define exception:unknown-sharp-object
@ -83,6 +84,30 @@
(equal? '(+ 2)
(read-string "(+ 2 #! a comment\n!#\n) ")))
(pass-if "R6RS/SRFI-30 block comment"
(equal? '(+ 1 2 3)
(read-string "(+ 1 #| this is a\ncomment |# 2 3)")))
(pass-if "R6RS/SRFI-30 nested block comment"
(equal? '(a b c)
(read-string "(a b c #| d #| e |# f |#)")))
(pass-if "R6RS/SRFI-30 block comment syntax overridden"
;; To be compatible with 1.8 and earlier, we should be able to override
;; this syntax.
(let ((rhp read-hash-procedures))
(dynamic-wind
(lambda ()
(read-hash-extend #\| (lambda args 'not)))
(lambda ()
(fold (lambda (x y result)
(and result (eq? x y)))
#t
(read-string "(this is #| a comment)")
`(this is not a comment)))
(lambda ()
(set! read-hash-procedures rhp)))))
(pass-if "unprintable symbol"
;; The reader tolerates unprintable characters for symbols.
(equal? (string->symbol "\001\002\003")
@ -131,6 +156,9 @@
(pass-if-exception "unterminated block comment"
exception:unterminated-block-comment
(read-string "(+ 1 #! comment\n..."))
(pass-if-exception "R6RS/SRFI-30 unterminated nested block comment"
exception:unterminated-block-comment
(read-string "(foo #| bar #| |#)"))
(pass-if-exception "unknown character name"
exception:unknown-character-name
(read-string "#\\theunknowncharacter"))