WRITE & linefeed

WRITE & linefeed

[Ian Price]

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Hello guilers,

There's a small aesthetic issue that's been bothering me for a
while. Namely, newlines aren't treated like other escape sequences when
printed with WRITE.

scheme@(guile-user)> (write "\n")
"
"scheme@(guile-user)>

Now, I can see why this would be useful when printing multiple line
strings, but the inconsistency with e.g. "\t\f" irks me. What do the
rest of you think?

I've also attached the patch I've been using to fix this for me.
-- 
Ian Price

"There are only two hard problems in Computer Science: cache invalidation
and naming things." - Phil Karlton


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From 81bf0d0a4c47b1146395fd9282c1fc2ac3d495d4 Mon Sep 17 00:00:00 2001
From: Ian Price <ianprice90@googlemail.com>
Date: Sun, 19 Jun 2011 12:30:26 +0100
Subject: [PATCH] use escape sequence when printing newlines with 'write'

* libguile/print.c (write_character_escaped, write_character):
  Use '\n' escape sequence rather than the character 0xa0 when printing
  strings with WRITE.
---
 libguile/print.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libguile/print.c b/libguile/print.c
index 4afd12c..e215f3f 100644
--- a/libguile/print.c
+++ b/libguile/print.c
@@ -1022,7 +1022,7 @@ write_character_escaped (scm_t_wchar ch, int string_escapes_p, SCM port)
       static const char escapes[7] = "abtnvfr";
       char buf[9];
 
-      if (ch >= 0x07 && ch <= 0x0D && ch != 0x0A)
+      if (ch >= 0x07 && ch <= 0x0D)
 	{
 	  /* Use special escapes for some C0 controls.  */
 	  buf[0] = '\\';
@@ -1119,7 +1119,7 @@ write_character (scm_t_wchar ch, SCM port, int string_escapes_p)
 	  display_character (ch, port, strategy);
 	  printed = 1;
 	}
-      else if (ch == ' ' || ch == '\n')
+      else if (ch == ' ')
 	{
 	  display_character (ch, port, strategy);
 	  printed = 1;
-- 
1.7.5.4

Re: WRITE & linefeed

[Neil Jerram]

Ian Price <ianprice90@googlemail.com> writes:

> Hello guilers,
>
> There's a small aesthetic issue that's been bothering me for a
> while. Namely, newlines aren't treated like other escape sequences when
> printed with WRITE.
>
> scheme@(guile-user)> (write "\n")
> "
> "scheme@(guile-user)>
>
> Now, I can see why this would be useful when printing multiple line
> strings, but the inconsistency with e.g. "\t\f" irks me. What do the
> rest of you think?

I agree, but I can imagine that there is a case for the current
behaviour too, and it's nice to preserve back-compatibility.  Emacs has
`print-escape-newlines', and I guess we need something like that here -
an addition to `print-options'?

       Neil

Re: WRITE & linefeed

[Andy Wingo]

Hi,

On Wed 22 Jun 2011 23:49, Neil Jerram <neil@ossau.uklinux.net> writes:

> Ian Price <ianprice90@googlemail.com> writes:
>
>> There's a small aesthetic issue that's been bothering me for a
>> while. Namely, newlines aren't treated like other escape sequences when
>> printed with WRITE.
>>
>> scheme@(guile-user)> (write "\n")
>> "
>> "
>
> I agree, but I can imagine that there is a case for the current
> behaviour too, and it's nice to preserve back-compatibility.  Emacs has
> `print-escape-newlines', and I guess we need something like that here -
> an addition to `print-options'?

Good idea.  I implemented this, and will push by the time you get this
mail.  The default is to escape newlines.

Andy
-- 
http://wingolog.org/