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sorry guys i apologize for this question,

how come when writing a program that these are not equivalent:

[at] files = readdir(D);

vs

readdir(D) = [at] files;


thanks for your patience,
stace

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Hi Stace!

On Sunday 28 Feb 2010 20:14:57 S O wrote:
> sorry guys i apologize for this question,
>
> how come when writing a program that these are not equivalent:
>
> [at] files =3D readdir(D);
>
> vs
>
> readdir(D) =3D [at] files;
>

Well, first of all, use strict and warnings and use lexical filehandles and=

dirhandles.

Otherwise the "A =3D B" sets A to the value of the expression B (and never =
vice-
versa). "my [at] files =3D readdir($dir_handle);" assigns what readdir returns =
(in
list context) to [at] files, and populates [at] files with the contents of the
directory. But setting =ABreaddir($dir_handle)=BB with some value is not pe=
rmitted
by Perl and I'm not sure what it will do.

=46or more information, see the section about lvalues and rvalues here:

http://en.wikipedia.org/wiki/Value_%28computer_science%29

Regards,

Shlomi Fish

>
> thanks for your patience,
> stace

=2D-
=2D--------------------------------------------------------- -------
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>>>>> "SO" == S O <shogunok [at] gmail.com> writes:

SO> sorry guys i apologize for this question,
SO> how come when writing a program that these are not equivalent:

SO> [at] files = readdir(D);

SO> vs

SO> readdir(D) = [at] files;

my question is why would you think they are the same? your same question
can be asked about $x = $y vs $y = $x. do you know what = means in perl
(and almost all common programming languages)?

uri

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On Sunday 28 Feb 2010 22:08:21 Uri Guttman wrote:
> >>>>> "SO" == S O <shogunok [at] gmail.com> writes:
> SO> sorry guys i apologize for this question,
> SO> how come when writing a program that these are not equivalent:
>
> SO> [at] files = readdir(D);
>
> SO> vs
>
> SO> readdir(D) = [at] files;
>
> my question is why would you think they are the same? your same question
> can be asked about $x = $y vs $y = $x. do you know what = means in perl
> (and almost all common programming languages)?
>

Now that I think about it, I think they may be confusing it with "=="
(numerical equality). So:

20 + 4 == 24

Is indeed equivalent to:

24 == 20 + 4

But naturally "=" is assignment instead of equality.

Regards,

Shlomi Fish


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