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Re: two + 2 not equal 4!

by toolic (Bishop)
on Jul 24, 2010 at 02:09 UTC ( #851103=note: print w/replies, xml ) Need Help??

in reply to two + 2 not equal 4!

Tip #6 from the Basic debugging checklist: use B::Deparse to see if your code really is what you think it is:
$ perl -MO=Deparse BEGIN { $^W = 1; } sub two { use strict 'refs'; 2; } use strict 'refs'; printf "two + 2 = %d\n", two(2);

So, two + 2 is interpreted as two(2). Instead of evaluating your function, then adding 2, perl treats everything after your function call as a LIST of arguments when you omit the parentheses. From perlsub:

2. NAME LIST; # Parentheses optional if predeclared/imported.

While it is legal syntax to omit the parentheses on function calls, it is a good practice to use them, even if your function does not need arguments:

printf "two + 2 = %d\n",two() + 2;

As a side note, your code would render better if you replace your "pre" tags with "code" tags: Writeup Formatting Tips

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[PriNet]: quick question... anyone know how to remove all the existing keys in a %hash ? i've tried several options, but when i re-use the hash, some of the "upper" keys that i don't re-use stick and i can't get them to "remove"
[atcroft]: PriNet: %hash = ();? or foreach my $k ( keys %hash ) { delete $hash{$k}; }?

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