bug#13394: Misalignment for "seq -w"

[Pádraig Brady]

On 01/09/2013 11:01 AM, Erik Auerswald wrote:
> Hi,
>
> On 01/09/2013 11:34 AM, Bernhard Voelker wrote:
> > On 01/09/2013 11:14 AM, Marcel Böhme wrote:
> > > There are the following problems with the -w parameter of the seq tool:
> > > [...]
> >
> > Hmm, according to the TEXI manual, the FIRST number should also use
> > a fixed point decimal representation when the -w option is used:
> > [...]
> > But that leaves the question open if there's a reason for this.
> > I.e. if it's just documented behavior, a requirement of some
> > standard or due to compatibility reasons.
>
> That seems to be just documented behavior, since seq is not standardized by 
> POSIX and other seq implementations ([1],[2],[3]) don't document this. On the 
> contrary, a common example is 'seq -w 0 .05 .1'.
>
> This example works fine with GNU seq:
>
> $ seq -w 0 .05 .1
> 0.00
> 0.05
> 0.10
>
> Even when counting to negative numbers:
>
> $ seq -w 0 -.05 -.1
> 00.00
> -0.05
> -0.10
>
> Starting with a negative number with a fractional step size breaks equal width 
> for non-negative numbers:
>
> $ seq -w -1 .5 1
> -1.0
> -0.5
> 0.0
> 0.5
> 1.0
>
> $ seq --version | head -n1
> seq (GNU coreutils) 8.13

Looks like a bug. I'll fix with:

diff --git a/src/seq.c b/src/seq.c
index e1b467c..3eb53f8 100644
--- a/src/seq.c
+++ b/src/seq.c
@@ -332,6 +332,8 @@ get_default_format (operand first, operand step, operand 
last)
             last_width--;  /* don't include space for '.' */
           if (last.precision == 0 && prec)
             last_width++;  /* include space for '.' */
+          if (first.precision == 0 && prec)
+            first_width++;  /* include space for '.' */
           size_t width = MAX (first_width, last_width);
           if (width <= INT_MAX)
             {