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My rule of thumb: if a function doesn't make code any easier to read, it's not worth writing.

At one point in my life (not very long ago ;)), I had the temptation to create lots of little 2-line and 3-line functions (probably coming from an OO background in school, where I was taught to make even simple variable accesses into object methods...)

But, consider the following code:

# test1.pl (uses no user-defined functions): for($i = 0; $i < 100000; $i++) { print $i; } # test2.pl (uses a simple function): for($i = 0; $i < 100000; $i++) { print func($i); } sub func { return $_[0]; } # OUTPUT [falkkin@shadow ~/perl] time perl test1.pl > /dev/null real 0m4.826s user 0m4.240s sys 0m0.010s [falkkin@shadow ~/perl] time perl test2.pl > /dev/null real 0m14.227s user 0m14.100s sys 0m0.050s

It's clear in this case that the overhead involved in calling a function (mostly involving pushing variables to perl's stack and popping them back off) makes the code run roughly 3 times more slowly. Generally, I try to avoid calls to "small" functions in inner loops whenever performance is anything of an issue; if I'm only reusing those few lines of code once or twice in a program, it's just not worth it to create a function for it, in my opinion.


In reply to Re: When do you function? by Falkkin
in thread When do you function? by zdog

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