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Re: Re: Check on if statement

by BrowserUk (Patriarch)
on Aug 17, 2002 at 19:11 UTC ( [id://190904]=note: print w/replies, xml ) Need Help??


in reply to Re: Check on if statement
in thread Check on if statement

I don't think defined() is gonna work. That will be true if $foo has any value and will short-circuit the regex....


What's this about a "crooked mitre"? I'm good at woodwork!

Replies are listed 'Best First'.
defined() might be a good idea
by BronzeWing (Monk) on Aug 17, 2002 at 20:09 UTC

    I think defined() is a good idea if there's a possibility of $foo being undefined, so as to avoid a warning about an undef being used in a string comparison/regex. Assuming an undefined value counts as a blank, I would write it like this:

    if (!defined($foo) or $foo =~ m/^\??$/) { # Foo is valid }

    Thus: "If foo is undefined, or matches an empty string or a single question mark."

    But wasn't there something about \n's counting as "^" and/or "$"? Hmmm...


    The Secret to Fortune Cookies in One Line
    print join("... in bed", `fortune fortunes` =~ m/^(.*)(\.|\?|\!)$/), "\n";

      I wasn't saying that defined() doesn't have important uses, only that it use as given in the referenced post was not useful.

      That said, I wouldn't use a regex as you have either. You point out one reason yourself, though m//s would probably address that concern, but, as others pointed out earlier, using a regex to test a string against a single, predefined char (or word)--especially when that char is a non-word char, meaning that the m//i option would be of no benefit--is simply overkill.

      Personally, I would probably code the test as:

      if ( !defined($foo) or $foo eq '' or $foo eq '?' ) { print "\$foo OK!\n"; }

      as using a regex against a fixed string seems pointless and I prefer positive conditions to negative ones.

      Update:Modified condition, struck irrelevant comments. Seems I lost track of the original questioners reqs. Personally, I probably still wouldn't use a regex for this.


      What's this about a "crooked mitre"? I'm good at woodwork!
        I havent read the rest of the thread, I only comment because of your mistake in the cb ;-), but the test you describe:
        if ( defined($foo) and $foo eq '?' ) { print "\$foo OK!\n"; }
        Would be better (Lazier) written
        print "\$foo OK!\n" if $foo and $foo eq '?';
        in my opinion anyway...

        Note that since $foo must be a '?', then it cant be _any_ false value, defined being only one of three. Thus you can dispose of the defined test and replace it with simple true or false.

        Yves / DeMerphq
        ---
        Software Engineering is Programming when you can't. -- E. W. Dijkstra (RIP)

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