GNU bug report logs - #9664
(format #t "~3tX") fails in the REPL

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: rixed <at> happyleptic.org
To: bug-guile <at> gnu.org
Subject: (format #t "~3tX") fails in the REPL
Date: Mon, 3 Oct 2011 21:59:48 +0200

The ~t formater is not working according to spec in the REPL.
Try this for instance:

(format #t "~10tA~20tB~30tC~40tD")

will print:

AB       C         D

Although it works from a script or when outputing to a sting.

Also, it works after a newline.

Message #8 received at 9664 <at> debbugs.gnu.org (full text, mbox):

From: Ian Price <ianprice90 <at> googlemail.com>
To: 9664 <at> debbugs.gnu.org
Subject: bug#9664: (format #t "~3tX") fails in the REPL
Date: Tue, 04 Oct 2011 11:59:11 +0100

[Message part 1 (text/plain, inline)]

When an expression is evaluated, the port-column is not 0. You can see
this by typing (write (port-column (current-output-port))) at the
repl. This means that when you do ~3t, it will not generate any spaces
as it is already past column 3.

This can be fixed by resetting port-position before we evaluate the REPL
expression.

-- 
Ian Price

"Programming is like pinball. The reward for doing it well is
the opportunity to do it again" - from "The Wizardy Compiled"

[0001-Reset-port-column-before-evaluating-at-REPL.patch (text/x-patch, inline)]

From 7a457be8c43051817b18d425a76b296f0f1fc730 Mon Sep 17 00:00:00 2001
From: Ian Price <ianprice90 <at> googlemail.com>
Date: Tue, 4 Oct 2011 00:30:39 +0100
Subject: [PATCH] Reset port column before evaluating at REPL.

* module/system/repl/repl.scm (run-repl): Column-dependant commands
  like the '~t' directive to format behave unexpectedly if column
  number isn't reset.
---
 module/system/repl/repl.scm |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/module/system/repl/repl.scm b/module/system/repl/repl.scm
index 1cffa71..d028f38 100644
--- a/module/system/repl/repl.scm
+++ b/module/system/repl/repl.scm
@@ -190,6 +190,7 @@
                                (run-hook before-eval-hook exp)
                                (call-with-error-handling
                                 (lambda ()
+                                  (set-port-column! (current-output-port) 0)
                                   (with-stack-and-prompt thunk))
                                 #:on-error (repl-option-ref repl 'on-error)))
                              (lambda (k) (values))))
-- 
1.7.6.4

Message #11 received at 9664 <at> debbugs.gnu.org (full text, mbox):

From: Andy Wingo <wingo <at> pobox.com>
To: rixed <at> happyleptic.org
Cc: 9664 <at> debbugs.gnu.org
Subject: Re: bug#9664: (format #t "~3tX") fails in the REPL
Date: Wed, 05 Oct 2011 20:18:26 +0200

On Mon 03 Oct 2011 21:59, rixed <at> happyleptic.org writes:

> The ~t formater is not working according to spec in the REPL.
> Try this for instance:
>
> (format #t "~10tA~20tB~30tC~40tD")
>
> will print:
>
> AB       C         D
>
> Although it works from a script or when outputing to a sting.
>
> Also, it works after a newline.

It appears that there is some difference between the readline-enabled
reader and the normal one.

    $ meta/guile -q
    scheme@(guile-user)> (port-column (current-output-port))
    $1 = 21

It is 0 with the readline reader.

I don't think the set-port-column! fix is right.  Why is the newline not
being chomped after the `(read)', I wonder?

Andy
-- 
http://wingolog.org/

Message #16 received at 9664-done <at> debbugs.gnu.org (full text, mbox):

From: Andy Wingo <wingo <at> pobox.com>
To: rixed <at> happyleptic.org
Cc: 9664-done <at> debbugs.gnu.org
Subject: Re: bug#9664: (format #t "~3tX") fails in the REPL
Date: Wed, 16 Nov 2011 23:15:00 +0100

On Wed 05 Oct 2011 20:18, Andy Wingo <wingo <at> pobox.com> writes:

> It appears that there is some difference between the readline-enabled
> reader and the normal one.
>
>     $ meta/guile -q
>     scheme@(guile-user)> (port-column (current-output-port))
>     $1 = 21
>
> It is 0 with the readline reader.
>
> I don't think the set-port-column! fix is right.  Why is the newline not
> being chomped after the `(read)', I wonder?

That isn't the right question, it turns out.  21 is the length of the
`scheme@(guile-user)> ' prompt.  We need to set the output port column
to 0 after printing a prompt.  In the readline case it's different
because readline is the part that prints the prompt.

Fixed in stable-2.0.

Thanks for the report,

Andy
-- 
http://wingolog.org/

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