Re: r6rs incompatibilities

[Julian Graham <joolean@gmail.com>]

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Hello again!


>  * I'm sure there are other points -- please test and reply :)

Indeed!

One thing I noticed while look at Andreas' `wak' project is that the
use of `#!r6rs' seems to be pretty common, which conflicts with
Guile's support for SCSH-style block comments.  Find attached a
(somewhat inelegant) patch that adds support for the `#!r6rs' lexeme
in the default reader.  (What do people think about this?  Is there a
better way to do it?)


Regards,
Julian

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From f1af40142b47232e726cbe9f7bdc35d5fbf45602 Mon Sep 17 00:00:00 2001
From: Julian Graham <julian.graham@aya.yale.edu>
Date: Sun, 23 May 2010 11:24:59 -0400
Subject: [PATCH] Support for the #!r6rs lexeme.

* libguile/read.c (scm_read_shebang): New function;
  (scm_read_sharp): Call scm_read_shebang on '!', which delegates to
  scm_read_scsh_block_comment as necessary.
---
 libguile/read.c |   39 +++++++++++++++++++++++++++++++++++++--
 1 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/libguile/read.c b/libguile/read.c
index c54fbb6..d169167 100644
--- a/libguile/read.c
+++ b/libguile/read.c
@@ -189,6 +189,7 @@ static SCM *scm_read_hash_procedures;
 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_read_shebang (scm_t_wchar, SCM);
 static SCM scm_get_hash_procedure (int);
 
 /* Read from PORT until a delimiter (e.g., a whitespace) is read.  Put the
@@ -309,7 +310,7 @@ flush_ws (SCM port, const char *eoferr)
 	    eoferr = "read_sharp";
 	    goto goteof;
 	  case '!':
-	    scm_read_scsh_block_comment (c, port);
+	    scm_read_shebang (c, port);
 	    break;
 	  case ';':
 	    scm_read_commented_expression (c, port);
@@ -1109,6 +1110,40 @@ scm_read_scsh_block_comment (scm_t_wchar chr, SCM port)
   return SCM_UNSPECIFIED;
 }
 
+static inline SCM
+scm_read_shebang (scm_t_wchar chr, SCM port)
+{
+  int c = 0;
+  if ((c = scm_get_byte_or_eof (port)) != 'r')
+    {
+      scm_ungetc (c, port);
+      return scm_read_scsh_block_comment (chr, port);
+    }
+  if ((c = scm_get_byte_or_eof (port)) != '6')
+    {
+      scm_ungetc (c, port);
+      scm_ungetc ('r', port);
+      return scm_read_scsh_block_comment (chr, port);
+    }
+  if ((c = scm_get_byte_or_eof (port)) != 'r')
+    {
+      scm_ungetc (c, port);
+      scm_ungetc ('6', port);
+      scm_ungetc ('r', port);
+      return scm_read_scsh_block_comment (chr, port);
+    }
+  if ((c = scm_get_byte_or_eof (port)) != 's')
+    {
+      scm_ungetc (c, port);
+      scm_ungetc ('r', port);
+      scm_ungetc ('6', port);
+      scm_ungetc ('r', port);
+      return scm_read_scsh_block_comment (chr, port);
+    }
+  
+  return SCM_UNSPECIFIED;
+}
+
 static SCM
 scm_read_r6rs_block_comment (scm_t_wchar chr, SCM port)
 {
@@ -1323,7 +1358,7 @@ 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));
+      return (scm_read_shebang (chr, port));
     case ';':
       return (scm_read_commented_expression (chr, port));
     case '`':
-- 
1.7.0.4