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Using $a and $b for temporary vars are bad form for our example,
as they have special meaning in Perl.

Index: plperl.sgml
================================================== =================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/plperl.sgml,v
retrieving revision 2.46
diff -r2.46 plperl.sgml
121,124c121,124
< my ($a,$b) = @_;
< if (! defined $a) {
< if (! defined $b) { return undef; }
< return $b;
---
> my ($x,$y) = @_;
> if (! defined $x) {
> if (! defined $y) { return undef; }
> return $y;
126,128c126,128
< if (! defined $b) { return $a; }
< if ($a &gt; $b) { return $a; }
< return $b;
---
> if (! defined $y) { return $x; }
> if ($x &gt; $y) { return $x; }
> return $y;

--
Greg Sabino Mullane greg@turnstep.com
PGP Key: 0x14964AC8 200510181742
http://biglumber.com/x/web?pk=2529DF...9B906714964AC8

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Patch applied, thanks. I actually told somebody off roundly about this
not long ago.

cheers

andrew

Greg Sabino Mullane wrote:

>
>Using $a and $b for temporary vars are bad form for our example,
>as they have special meaning in Perl.
>
>
[snip]


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"Greg Sabino Mullane" <greg@turnstep.com> writes:
> Using $a and $b for temporary vars are bad form for our example,
> as they have special meaning in Perl.

Please, tell me that isn't so. $a is a reserved name now? What was
Larry thinking?

regards, tom lane

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Tom Lane asked:

> Please, tell me that isn't so. $a is a reserved name now? What was
> Larry thinking?

It's not that bad, really. $a and $b have special meaning inside of
a sort subroutine as the two items being compared. Thus, you can write
something like this:

my @crooks = sort { lc $a cmp lc $b } @whitehouse;

to create a list sorted by lowercase (albeit not in the most efficient
matter). This will work even with "use strict" turned on, as $a and $b
will not trip Perl's strict-mode checking of undeclared variables. So,
the danger is very minor, but it's a good practice to not use them for
temporary variables in a script.

- --
Greg Sabino Mullane greg@turnstep.com
PGP Key: 0x14964AC8 200510182220
http://biglumber.com/x/web?pk=2529DF...9B906714964AC8

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Greg Sabino Mullane wrote:

>Tom Lane asked:
>
>
>
>>Please, tell me that isn't so. $a is a reserved name now? What was
>>Larry thinking?
>>
>>
>
>It's not that bad, really. $a and $b have special meaning inside of
>a sort subroutine as the two items being compared. Thus, you can write
>something like this:
>
>my @crooks = sort { lc $a cmp lc $b } @whitehouse;
>
> to create a list sorted by lowercase (albeit not in the most efficient
>matter). This will work even with "use strict" turned on, as $a and $b
>will not trip Perl's strict-mode checking of undeclared variables. So,
>the danger is very minor, but it's a good practice to not use them for
>temporary variables in a script.
>
>
>
>

I recently lost quite some time tracking down a piece of spurious data
persistence that eventually turned out to be due to use of an undeclared
$a that strict mode failed to detect, so it's not so minor, really.

In retrospect, the choice of names for sort comparison operands was
poor, as I suspect Larry would agree, but it's been there ever since I
have been using perl (around 12 years now, iirc).

cheers

andrew

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