Re: [bug-gawk] Documentation

[Manuel Collado]

El 10/12/2014 2:36, Andrew J. Schorr escribió:
> On Tue, Dec 09, 2014 at 02:35:28PM -0500, Teri Price wrote:
> > In section 9.1.1 of the documentation, there is an example that I think has
> > a mistake.
> > Here's the example:
> > "
> > i = 5
> > j = atan2(i++, i *= 2)
> >
> > If the order of evaluation is left to right, then i first becomes 6, and
> > then 12, and atan2() is called with the two arguments 6 and 12. But if the
> > order of evaluation is right to left, i first becomes 10, then 11, and
> > atan2() is called with the two arguments 11 and 10.
> > "
> >
> > And here's what I think it should be:
> >
> > If the order is left to right, atan2 is called with 2 arguments 5 and 12
> > because i++ has the value of 5 even though i became 6.
> >
> > If the order is right to left, i*=2 makes i 10 and then i++ still holds the
> > value 10, so the 2 arguments would be 10 and 10.
>
> I think you are correct.  But isn't the simpler fix to replace "i++"
> with "++i"? :-)

When calling a function, using expressions with side effects as 
arguments can be considered unsafe. At least if the evaluation of some 
argument affects the evaluation of others. To be safe you could write:

i = 5
a = i++
b = i *= 2
j = atan2(a, b)

Well, this is perhaps an academic point of view.

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