Re: [gawk] Change in the order of precedence for the redirection operator?

[Stepan Kasal]

Hello Arnold,

I cannot fully agree with the reasons you mentioned.  First, about *pars1.patch:

> > gawk-20051027-pars1.patch is a small cleanup of the grammar, [...]

> I am inclined at the moment not to accept the patches.  They add considerable
> complexity to the grammar to fix what is, in my opinion, a corner case, [...]

I agree that the "bug" fixed by *pars1.patch has zero weight.

If the patch has any value, then it is that it actually _simplifies_ the
grammar:  the special rule for "! regex" is now gone.

awkgram.y can be made shorter by replacing the code for Node_not by the
straightforward:
        { $$ = node($2, Node_not, (NODE *) NULL); }

I believe the performace hit would be minimal.
See the attached gawk-20051031-pars1a.patch.

Regarding the second of my patches:

On Fri, Oct 28, 2005 at 07:24:44AM +0200, Aharon Robbins wrote:
> > > > gawk 'BEGIN { "echo " "date" | getline;  print }'
...
> The problem is that the above is inherently ambiguous, [...]

Yes, it is, in POSIX awk.

But the gawk documentation contains "redirection" in the precedence table.
I believe this forms kind of promise how the above expression will work.

That is why I regretted that I talked you into breaking the backward
compatibility in 3.1.2.  (I even recall that I considered the possibility
to "shadow" some nonterminals, and dismissed it as overcomplicated.)

When I thought about it again, I recognized that the pars2.patch was too
complicated; the same can be achieved by adding only one nonterminal.

Attached please find gawk-20051031-pars2a.patch.

Please (re)consider this patch, too.

Have a nice day,
        Stepan Kasal

gawk-20051031-pars1a.patch
Description: Text document

gawk-20051031-pars2a.patch
Description: Text document