Re: Regex question

If you use a regex, you're going to have to quotemeta one of the strings because '.' is a meta (regex command) character.

If you use substr, you'll have problems if the length of the part you are trying to match can vary. Ie. Could the strings be '13.2.3' & '13.2' for example.

Using index will allow you to avoid both these problems. You simple want to know if the shorter string matches the longer string at position 0:

$var1 = '1.1.2'; 
$var2 = '1.1'; 
if( index( $var1, $var2 ) == 0 ) { 
    print "matches" 
} else { 
    print "Doesn't match" 
}
[download]

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

Comment on Re: Regex question Download Code

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Re^2: Regex question by Skeeve (Parson) on May 22, 2007 at 12:44 UTC
~~This will never match and is completly wrong as you mixed up $var1 and $var2.~~ ~~It should be~~ ~~`index( $var2, $var1 ) == 0`~~ ~~but this will still be~~ wrong because `$var2='1.11.2'; $var1='1.1';` [download] would give you a false match `s$$([},&%#}/&/]+}%&{});#$&&s&&$^X.($'^"%]=\&(\|?{%` `+`.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e	[reply] [d/l] [select]
Re^3: Regex question by BrowserUk (Patriarch) on May 22, 2007 at 13:42 UTC
This will never match and is completly wrong as you mixed up $var1 and $var2. Um, no. `C:\parrot>p1 [0] Perl> $var1 = '1.1.2'; $var2 = '1.1'; if( index( $var1, $var2 ) == 0 ) { print "matches" } else { print "Doesn't match" };; matches [0] Perl> $var1 = '1.1.2'; $var2 = '1.1'; if( index( $var2, $var1 ) == 0 ) { print "matches" } else { print "Doesn't match" };; Doesn't match` [download] but this will still be wrong because `$var2='1.11.2'; $var1='1.1';` [download] would give you a false match That's a good catch though. It's also easily fixed: `[0] Perl> $var1 = '1.11.2'; $var2 = '1.1'; if( index( $var1, "$var2." ) == 0 ) { print "matches" } else { print "Doesn't match" };; Doesn't match` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l] [select]
Re^4: Regex question by Skeeve (Parson) on May 22, 2007 at 22:47 UTC
Indeed! I mixed it up, not you. But your fix doesn't help with: `$var2='1.1'; $var1='1.1';` [download] It will give you a false negative ;-) See my solution above which handle both cases. `s$$([},&%#}/&/]+}%&{});#$&&s&&$^X.($'^"%]=\&(\|?{%` `+`.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e	[reply] [d/l] [select]