Re: matching patterns - - - EXPLANATION
"R. Joseph Newton" wrote:
Sorry Diego,
Turns out that there was a logic error in the code I posted that gave a false positive
on the match.
> #!perl -w
>
> use strict;
> use warnings;
>
> my $pat1 = qr /Hi.*?\sBye/;
> # my $pat2 = qr /(Hi|[Hh]ello).*?\sBye--I'll sure miss you\!/; # Error
This does not work. Becuase the space escape is not a ltieral space the smaller regex
being matched against it wwill actually reject the match. This is corrected by
changing the escape here to a literal space:
my $pat2 = qr /(Hi|[Hh]ello).*?\sBye--I'll sure miss you\!/;
> print "$pat1 is the \"smaller\" pattern\n";
> print "$pat2 is the \"larger\" pattern\n";
> print "\n";
>
> if ($pat2 =~ $pat1) {
> print "$pat2 contains $pat1\n";
> } else {
> # print "$pat2 matches $pat1\n"; # False match generator
> }
> print "\n";
Corrected as:
if ($pat2 =~ $pat1) {
print "$pat2 matches $pat1\n";
} else {
print "$pat2 does not match $pat1\n";
}
print "\n";
With the corrections noted, the code does provide the same output as the original,
differing only in the content of the second regex. I think the following should give
a pretty accurate picture of whether one compiled regex is a true subpattern of the
other, although it would take more work to identify subpatterns which originate within
the larger regex, rather than at the same origin:
> my $test = $pat1;
> chop $test; # kill the closing paren of the canonical regex
> if ($test eq substr($pat2, 0, length($test))) {
> print "$pat1 is a true sub-pattern of $pat2\n";
> } else {
> print "$pat1 could not be identified by this test as a true initial sub-pattern of
> $pat2\n";
> }
> print "\n";
>
> my $string1 = "Hello, Bye--I'll sure miss you!";
>
> if ($string1 =~ $pat1) {
> print "$string1 matches $pat1\n";
> } else {
> print "$string1 does not match $pat1\n";
> }
>
> if ($string1 =~ $pat2) {
> print "$string1 matches $pat2\n";
> } else {
> print "$string1 does not match $pat2\n";
> }
>
> Hi There,podner E:\d_drive\perlStuff>pat_holds.pl
> (?-xism:Hi.*?\sBye) is the "smaller" pattern
> (?-xism:(Hi|[Hh]ello).*?\sBye--I'll sure miss you!) is the "larger" pattern
>
> (?-xism:(Hi|[Hh]ello).*?\sBye--I'll sure miss you!) matches (?-xism:Hi.*?\sBye)
>
> (?-xism:Hi.*?\sBye) is not a true sub-pattern of (?-xism:(Hi|[Hh]ello).*?\sBye--
> I'll sure miss you!)
>
> Hello, Bye--I'll sure miss you! does not match (?-xism:Hi.*?\sBye)
> Hello, Bye--I'll sure miss you! matches (?-xism:(Hi|[Hh]ello).*?\sBye--I'll sure
> miss you!)
>
> Hi There,podner E:\d_drive\perlStuff>
>
> Joseph
>
> --
> To unsubscribe, e-mail: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: matching patterns - - - EXPLANATION
Diego Riano wrote:
> I am trying to put it in a better way, (I hope :-))
>
> What I am trying to do is check if two patterns could recognize the same
> string, for example:
> $pattern1=[ag]oprs[cd]x9;
> $pattern2=[agpr]oprs;
>
> these two patterns would recognize, both, a set of strings. however
> there will be some strings that only $pattern2 will match and viceversa.
> So, How can I compare these two patterns to say if they are similar or
> the same?
>
> thanks again
It would be somewhat difficult, I suspect. Perhaps by taking substrings on their
canonical forms, after compiling to regex. Unfortunately, matching comparisions: do
not guarantee that one is actually a subpattern of the other. You already provided
the answer to that question when you indicated that their matching sets each had a
subset that was not contained in the union. Unfortunately, a pattern can match
another pattern without the other pattern being a sub-pattern:
#!perl -w
use strict;
use warnings;
my $pat1 = qr /Hi.*?\sBye/;
my $pat2 = qr /(Hi|[Hh]ello).*?\sBye--I'll sure miss you\!/;
print "$pat1 is the \"smaller\" pattern\n";
print "$pat2 is the \"larger\" pattern\n";
print "\n";
if ($pat2 =~ $pat1) {
print "$pat2 contains $pat1\n";
} else {
print "$pat2 matches $pat1\n";
}
print "\n";
my $test = $pat1;
chop $test; # kill the closing paren of the canonical regex
if ($test eq substr($pat2, 0, length($test))) {
print "$pat1 is a true sub-pattern of $pat2\n";
} else {
print "$pat1 is not a true sub-pattern of $pat2\n";
}
print "\n";
my $string1 = "Hello, Bye--I'll sure miss you!";
if ($string1 =~ $pat1) {
print "$string1 matches $pat1\n";
} else {
print "$string1 does not match $pat1\n";
}
if ($string1 =~ $pat2) {
print "$string1 matches $pat2\n";
} else {
print "$string1 does not match $pat2\n";
}
Hi There,podner E:\d_drive\perlStuff>pat_holds.pl
(?-xism:Hi.*?\sBye) is the "smaller" pattern
(?-xism:(Hi|[Hh]ello).*?\sBye--I'll sure miss you!) is the "larger" pattern
(?-xism:(Hi|[Hh]ello).*?\sBye--I'll sure miss you!) matches (?-xism:Hi.*?\sBye)
(?-xism:Hi.*?\sBye) is not a true sub-pattern of (?-xism:(Hi|[Hh]ello).*?\sBye--
I'll sure miss you!)
Hello, Bye--I'll sure miss you! does not match (?-xism:Hi.*?\sBye)
Hello, Bye--I'll sure miss you! matches (?-xism:(Hi|[Hh]ello).*?\sBye--I'll sure
miss you!)
Hi There,podner E:\d_drive\perlStuff>
Joseph
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Re: matching patterns - - - EXPLANATION
I am trying to put it in a better way, (I hope :-))
What I am trying to do is check if two patterns could recognize the same
string, for example:
$pattern1=[ag]oprs[cd]x9;
$pattern2=[agpr]oprs;
these two patterns would recognize, both, a set of strings. however
there will be some strings that only $pattern2 will match and viceversa.
So, How can I compare these two patterns to say if they are similar or
the same?
thanks again
On Thu, 2003-04-03 at 14:11, Diego Riano wrote:
> Hello All
>
> I am having problem figuring out how to match two patterns. I have two
> pattern and I would like to now if they are the same or if one of them
> is a sub pattern of the other. Ej:
> $pattern1=[agpr]oprs[cd]x9;
> $pattern2=[agpr]oprs;
> $pattern3=aors;
>
> $pattern2 is a "subpattern" of $pattern1, and $pattern3 is completely
> different form 1 or 2.
>
> I was trying with If ($paternn1=~/$pattern2/){do somthing . .. }
> put it just works if the left side is a string, with a pattern it does
> not work
>
> Some ideas??
>
> Thanks in advance
>
> Diego Riano
--
___
Diego Mauricio Riano Pachon
Biologist
Institute of Biology and Biochemistry
Potsdam University
Karl-Liebknecht-Str. 24-25
Haus 20
14476 Golm
Germany
Tel:0331/977-2809
http://bioinf.ibun.unal.edu.co/~gotem
http://www.geocities.com/dmrp.geo/
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
