Re: [bug-gawk] Postdecrementing $NF

[Andrew J. Schorr]

On Sun, Sep 08, 2013 at 02:56:52AM +0200, Adam Zieliński wrote:
> $NF-- (or even $(NF--) ) - doesn't seem to work as intended.

The '$' has higher priority then '--', so I believe $NF-- is equivalent to
($NF)--, which is effectively equivalent to $NF.

> Instead of giving me a field value and decrementing FN after that,
> it converts field value to number and then decrements it.
> 
> Doing the same via variable set to NF works perfectly.

However, there does appear to be a problem with $(NF--).  Using current
git sources:

   bash-4.1$ echo 1 2 3 4 | gawk '{x = $(NF--); print x; print NF}'

   3

Compare to:

   bash-4.1$ echo 1 2 3 4 | gawk '{x = $NF; NF--; print x; print NF}'
   4
   3

and

   bash-4.1$ echo 1 2 3 4 | gawk '{i = NF; x = $(i--); print x; print i}'
   4
   3

I don't see any errors from valgrind.  I haven't looked further for the
cause of this bug...

Regards,
Andy