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Re^2: var comparison

by nemesisgus (Acolyte)
on Sep 06, 2012 at 19:01 UTC ( #992166=note: print w/replies, xml ) Need Help??

in reply to Re: var comparison
in thread var comparison

Thanks MidLifeXis. I like the grep way.

Just... Why would you prefer the first option over using a regexp? This simplified example shows only two elements to compare but if there were more the expression could get quite long.

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Re^3: var comparison
by MidLifeXis (Monsignor) on Sep 06, 2012 at 19:19 UTC

    Clarity of intent.

    • The first indicates (to me) that you are doing a whole string comparison. There is only one thing that the eq operation is able to do.
    • The regexp opens the possibility that there is something more complex happening. Even in this simple case, I still would need to switch languages to verify that there was nothing else going on in the statement.

    Admittedly, in this case, it is not a very complex regexp, so it probably does not make much of a difference. If I am doing a full string comparison, I reach for eq. If I am matching a pattern, I reach for a regexp. It seems to me that any cue that you can give to the future-you reading your code is a good thing.

    Update: As far as what to do once it gets a number of comparisons, refactor the comparisons out into a subroutine with a descriptive name and call it.

    The following statement takes a bit to digest:

    ( $var eq 'a' || $var eq 'b' || $var eq 'c' || $var eq 'd' )

    where this replacement, at least to me, is much clearer:

    ( isAnAllowedCharacter( $var ) )

    This also allows you to change the definition of what a valid character (or whatever you are testing for) is without changing the code that is performing the test:

    sub isAnAllowedCharacter { my $testee = shift; ( $testee eq 'a' || ... ) # or perhaps %valid_characters = map { $_ => 1 } ( 'a' .. 'd' ); $valid_characters{ $testee }; # or even perhaps my $validation_service = Remote::Validation::Service->new(...); $validation_service->isValid( $testee ); }

    Update 2: Missed this one before:

    This simplified example shows only two elements to compare but if there were more the expression could get quite long.

    It seems to me that a regexp with many strings can be just as unreadable as a series of $var eq '...' comparisons. Whitespace (and /x on the regexp) can make a world of difference.


      You've convinced me, specially with the part of the "cue that you can give to the future-you reading" ;^). I totally agree with your reasons.

      And nice snippet of code. I don't need something so elaborated at the moment but I will backup it for the future.

      Thanks again.

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