On Wed, 07 Dec 2005, Jan Dubois wrote:
> Or you can define a normal subroutine:
>
> sub DATA_COLS () { $os eq 'X') ? 6 : 7 }
>
> assuming $os will not change during the lifetime of your program.
I just realize that I should have emphasized the importance of specifying
the empty prototype for the "constant" function. This makes a big difference
when you use it without parentheses:
my $foo = DATA_COLS + 1;
will be compiled as
my $foo = DATA_COLS() + 1;
If you didn't specify the prototype:
sub DATA_COLS { $os eq 'X') ? 6 : 7 }
then it would be compiled as
my $foo = DATA_COLS(+ 1);
effectively ignoring the "+ 1" part.
Demo:
C:\>perl -we"sub foo {5}; print foo + 1"
5
C:\>perl -we"sub foo () {5}; print foo + 1"
6
Cheers,
-Jan
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