Re: [bug-gawk] getline difference from gawk versions >=4.0.0

[Brian Kernighan]

Interesting.  It's not clear what the "right" answer is, since arguably
if there was no input value, nothing should be stored in the array and
thus the increment should not happen.  (This is a weak argument, of
course.)  In my case, it's definitely an artifact of implementation,
and it could easily be changed.

Getline should have been a function.

Brian

On Mon, 2 Apr 2012, address@hidden wrote:

> Greetings. Re this:
>
> > Date: Sun, 01 Apr 2012 11:49:33 +0100
> > From: Duncan Moore <address@hidden>
> > To: "address@hidden" <address@hidden>
> > Subject: [bug-gawk] getline difference from gawk versions >=4.0.0
> >
> > Hi
> >
> > b.awk:
> >
> > BEGIN {
> >    system("echo 1 > f")
> >    while ((getline a[++c] < "f") > 0) {}
> >    print c
> > }
> >
> > gawk -f b.awk
> >
> > Prior to gawk 4.0.0 this outputs:
> >
> > 1
> >
> > For 4.0.0 and 4.0.1 it outputs:
> >
> > 2
> >
> > Regards
> > Duncan Moore
>
> This is an interesting test case. I get different answers with different
> versions of awk. Brian Kernighan's awk prints 1, mawk prints 2.
>
> It is clearly an artifact of the implementation, although I think that
> in this case 2 is the correct answer; the expression creating the "lvalue"
> to be assigned for getline should be completely evaluated before getline
> is invoked, making getline act more like a function call.
>
> It is probably worth documenting this as Yet Another Dark Corner in
> the language.
>
> Thanks!
>
> Arnold