Hi Guilers,
I was looking at some SRFIs recently (specifically SRFIs 88, 89, and
90), and I noticed that Guile could support all three of them pretty
easily if the reader allowed self-quoting keywords in which the colon
comes at the end, a la SRFI-88. The default reader behavior is to
only parse tokens as keywords if they begin with #: (e.g., #:foo), but
you can modify this behavior by setting the reader option (keywords
'prefix), which gets you keywords that start with just the colon
(e.g., :foo). What if we added another reader option, say, (keywords
'postfix), which would recognize SRFI-88-style keywords?
I've attached a (slightly clumsy) patch against HEAD that adds this
functionality to read.c. I know this is unsolicited, but I think it'd
be fairly useful in terms of compatibility.
Regards,
Julian
Index: read.c
===================================================================
RCS file: /sources/guile/guile/guile-core/libguile/read.c,v
retrieving revision 1.128
diff -a -u -r1.128 read.c
--- read.c 17 Oct 2007 21:56:10 -0000 1.128
+++ read.c 2 Nov 2007 23:54:18 -0000
@@ -53,6 +53,7 @@
SCM_GLOBAL_SYMBOL (scm_sym_dot, ".");
SCM_SYMBOL (scm_keyword_prefix, "prefix");
+SCM_SYMBOL (scm_keyword_postfix, "postfix");
scm_t_option scm_read_opts[] = {
{ SCM_OPTION_BOOLEAN, "copy", 0,
@@ -62,7 +63,7 @@
{ SCM_OPTION_BOOLEAN, "case-insensitive", 0,
"Convert symbols to lower case."},
{ SCM_OPTION_SCM, "keywords", SCM_UNPACK (SCM_BOOL_F),
- "Style of keyword recognition: #f or 'prefix."},
+ "Style of keyword recognition: #f, 'prefix, or 'postfix."},
#if SCM_ENABLE_ELISP
{ SCM_OPTION_BOOLEAN, "elisp-vectors", 0,
"Support Elisp vector syntax, namely `[...]'."},
@@ -532,6 +533,8 @@
{
SCM result, str = SCM_EOL;
int overflow = 0;
+ int postfix = scm_is_eq (SCM_PACK (SCM_KEYWORD_STYLE), scm_keyword_postfix);
+
char buffer[READER_BUFFER_SIZE];
size_t read = 0;
@@ -549,12 +552,26 @@
{
str = scm_string_concatenate (scm_reverse_x (str, SCM_EOL));
result = scm_string_to_symbol (str);
+
+ if (postfix)
+ {
+ size_t l = scm_c_string_length (str) - 1;
+ if (l && scm_is_true (scm_char_eq_p (scm_c_string_ref (str, l),
+ SCM_MAKE_CHAR (':'))))
+ result = scm_from_locale_keywordn (scm_i_string_chars (str), l);
+ }
}
else
+ {
+
/* For symbols smaller than `sizeof (buffer)', we don't need to recur to
Scheme strings. Therefore, we only create one Scheme object (a
symbol) per symbol read. */
- result = scm_from_locale_symboln (buffer, read);
+ if (postfix && read > 1 && buffer[read - 1] == ':')
+ result = scm_from_locale_keywordn (buffer, read - 1);
+ else
+ result = scm_from_locale_symboln (buffer, read);
+ }
return result;
}
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