Re: [PATCH] R6RS-style block comments

[Andreas Rottmann <a.rottmann@gmx.at>]

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ludo@gnu.org (Ludovic Courtès) writes:

> Hi,
>
> Andreas Rottmann <a.rottmann@gmx.at> writes:
>
>> Attached is a patch that extends the read syntax to allow for #| ... |#
>> block comments.
>
> Are there objections to this patch?  If no, I’ll apply it.
>
> Note that it makes the reader understand this syntax by default, not via
> a read option.
>
I have attached an updated version of the patch which should apply
cleanly against current HEAD.


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From: Andreas Rottmann <a.rottmann@gmx.at>
Subject: [PATCH] Add support for #| ... |# comments

This syntax has been added by R6RS.

---
 NEWS            |    5 +++++
 libguile/read.c |   33 ++++++++++++++++++++-------------
 2 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/NEWS b/NEWS
index 66e21de..c2f3bdc 100644
--- a/NEWS
+++ b/NEWS
@@ -412,6 +412,11 @@ actually used this, this behavior may be reinstated via the
 #; comments out an entire expression.  See SRFI-62 or the R6RS for more
 information.
 
+** Additional syntax for block comments
+
+#| ... |# is now accepted syntax for block comments, in addition to
+#! ... !#.
+
 ** `make-stack' with a tail-called procedural narrowing argument no longer
    works (with compiled procedures)
 
diff --git a/libguile/read.c b/libguile/read.c
index 07c8d71..10ac08e 100644
--- a/libguile/read.c
+++ b/libguile/read.c
@@ -180,9 +180,9 @@ static SCM *scm_read_hash_procedures;
   (((_chr) == 'e') || ((_chr) == 's') || ((_chr) == 'f')	\
    || ((_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);
+/* Read an SCSH or R6RS block comment.  */
+static inline SCM scm_read_block_comment (scm_t_wchar chr, SCM port);
+static SCM scm_read_commented_expression (scm_t_wchar chr, SCM port);
 
 /* Read from PORT until a delimiter (e.g., a whitespace) is read.  Return
    zero if the whole token fits in BUF, non-zero otherwise.  */
@@ -284,7 +284,8 @@ flush_ws (SCM port, const char *eoferr)
 	    eoferr = "read_sharp";
 	    goto goteof;
 	  case '!':
-	    scm_read_scsh_block_comment (c, port);
+          case '|':
+	    scm_read_block_comment (c, port);
 	    break;
 	  case ';':
 	    scm_read_commented_expression (c, port);
@@ -963,9 +964,10 @@ scm_read_guile_bit_vector (scm_t_wchar chr, SCM port)
 }
 
 static inline SCM
-scm_read_scsh_block_comment (scm_t_wchar chr, SCM port)
+scm_read_block_comment (scm_t_wchar chr, SCM port)
 {
-  int bang_seen = 0;
+  int comment_char_seen = 0;
+  int comment_char = (int) chr;
 
   /* We can use the get_byte here because there is no need to get the
      locale correct when reading comments. This presumes that 
@@ -976,15 +978,19 @@ scm_read_scsh_block_comment (scm_t_wchar chr, SCM port)
       int c = scm_get_byte_or_eof (port);
 
       if (c == EOF)
-	scm_i_input_error ("skip_block_comment", port,
-			   "unterminated `#! ... !#' comment", SCM_EOL);
+        {
+          scm_i_input_error ("skip_block_comment", port,
+                             "unterminated `#~A ... ~A#' comment",
+                             scm_list_2 (SCM_MAKE_CHAR (comment_char),
+                                         SCM_MAKE_CHAR (comment_char)));
+        }
 
-      if (c == '!')
-	bang_seen = 1;
-      else if (c == '#' && bang_seen)
+      if (c == comment_char)
+	comment_char_seen = 1;
+      else if (c == '#' && comment_char_seen)
 	break;
       else
-	bang_seen = 0;
+	comment_char_seen = 0;
     }
 
   return SCM_UNSPECIFIED;
@@ -1163,7 +1169,8 @@ scm_read_sharp (scm_t_wchar chr, SCM port)
     case '{':
       return (scm_read_extended_symbol (chr, port));
     case '!':
-      return (scm_read_scsh_block_comment (chr, port));
+    case '|':
+      return (scm_read_block_comment (chr, port));
     case ';':
       return (scm_read_commented_expression (chr, port));
     case '`':
-- 
tg: (b25aa0b..) t/r6rs-block-comments (depends on: master)

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Regards, Rotty