Re: [bug-gawk] pretty-print eats parentheses

[Manuel Collado]

El 30/10/2014 5:03, Hermann Peifer escribió:
> Hi Arnold and others,
>
> Below a small observation which I made while trying to construct a
> string consisting of negative integers with FS in between.
>
> I'm on gawk from git, on OSX 10.10.
>
> Regards, Hermann
>
> PS: I had a feeling of "déjà vu", but this historical issue was slightly
> different:
> http://lists.gnu.org/archive/html/bug-gnu-utils/2009-08/msg00018.html
>
> -------
>
> # Does not work as I expected..
> $ gawk 'BEGIN{FS="|"; str = -8 FS -9 ; print str}'
> -8-9

The second minus sign is parsed as a subtract operator. The expression 
is evaluated as -8 (FS - 9). FS is converted to number before 
subtraction and later concatenation. The pretty printer gives:

$ gawk -o/dev/stdout 'BEGIN{FS="|"; str = -8 FS -9 ; print str}'
-8-9
        BEGIN {
                FS = "|"
                str = -8 FS - 9
                print str
        }

> # ..but this does
> $ gawk 'BEGIN{FS="|"; str = -8 FS (-9) ; print str}'
> -8|-9

Now the second minus sign is parsed as part of a negative numeric 
constant. There is no subtract operator, just a concatenation one.

> # My parentheses are gone :-(
> $ gawk -o/dev/stdout 'BEGIN{FS="|"; str = -8 FS (-9) ; print str}'
> BEGIN {
>      FS = "|"
>      str = -8 FS -9
>      print str
> }

This is really weird. In any case please note the difference "- 9" vs 
"-9" in the prettied code for both cases.

Hope this helps. Regards.

--
Manuel Collado - http://lml.ls.fi.upm.es/~mcollado