Re^2: Why is const x const not a const?

[moritz]

The original question isn't phrased very carefully, but it does have an interesting core.

Perl has a "peephole optimizer" which evaluates some constant expressions at compile time. You can see that for example here:

$ perl -c -wE '1+1; say "OH HAI"'
Useless use of a constant (2) in void context at -e line 1.
-e syntax OK

Note that the -c switch means that the code is only compiled, not run. And yet the warning mentions 2 instead of 1+1, so you can see that the expression 1+1 has been evaluated at compile time, not at run time.

The original question could thus be phrase "Why is the expresion "literal" x <literal_number> not constant-folded at compile time, as <literal_number> + <literal_number> is?"

And yes, that's a valid and interesting question

I think if you want a constant use a constant

That's not very convincing. For example if I write '=' x 80, I see immediately that it's 80 equal signs. But if I write '===============================================================================', can you see immediately how many equal signs that are?

The difference in readability is even larger when whitspaces are concerned, ' ' x 20 vs. '                    '. Imagine that being printed out on a sheet of paper. Which one do you find easier to decipher?

[BrowserUk]

That's not very convincing. For example if I write '=' x 80, I see immediately that it's 80 equal signs. But if I write ...

You can do:

use constant EQUALx80 => '=' x 80;
...

[TomDLux]

Better, name it after its use, rather than its constituents.

use Readonly;
Readonly my $SECTION_SEPARATOR => q{=}x80;

[BrowserUk]

No. You are absolutely wrong on all counts!

First. Look at the post I was responding to. The premise was, that it is much clearer from '=' x 80 that there are 80 '=' than if you used

==================================================================

so your 'correction' is wrong in context.

Secondly, your assumption that that string is a "SECTION_SEPERATOR" is wrong. It cannot be right, because you have no basis upon which to reach that conclusion.

But mostly, trading use constant for that vacuous, puerile, slow, stupid, braindead, idiotic, stupid -- did I say stupid already? -- worthless, pathetic, fscked-up, oxymoronic piece of crap is ... um .. oh dear, I seems to have run out of appropriate adjectives.

Update: Oooh. OOoh! I thought of one: fatuous. ( I didn't use that already did I? )