string matching specific number of times

[tester]

Hi All,

My CPU taking 100% if I try to match more than the existing number of
specific matches in a string. Script is ...

my $something = "this is a test, just test, no kidding, small test, but
error in test. over over";
if ($something =~ m/((.*)test(.*)){5}/){
print "number of matches are 5, successful";
}
else{
print "no 5 matches, failure";
}

String "test" is repeated only 4 times in $something but if I am trying
to check whether the $something has 5, my CPU taking 100%. What is the
issue?

Thanks,
tester

 

[Paul Lalli]

My CPU taking 100% if I try to match more than the existing number of
specific matches in a string. Script is ...

my $something = "this is a test, just test, no kidding, small test, but
error in test. over over";
if ($something =~ m/((.*)test(.*)){5}/){
print "number of matches are 5, successful";

Instead of forcing the regexp engine took look for all the .*
repeatedly, why not just determine how many instances of 'test' there
are, and compare that to the number you want?

my @tests = $something =~ /test/g;
if (@tests == 5){
print "Success\n";
} else {
print "Failed, found " . @tests . " copies of 'test'\n";
}

Paul Lalli

 

[Tad McClellan]

if ($something =~ m/((.*)test(.*)){5}/){
print "number of matches are 5, successful";

To be accurate, that should be:

print "number of matches is at least 5, successful";

 

[ced]

Instead of forcing the regexp engine took look for all the .*
repeatedly, why not just determine how many instances of 'test' there
are, and compare that to the number you want?

my @tests = $something =~ /test/g;
if (@tests == 5){
print "Success\n";
} else {
print "Failed, found " . @tests . " copies of 'test'\n";
}

Or, simply:

my $count = 0;
$count++ while $something =~ /test/g;
....
else {
print "Failed, found $count copies of 'test'\n";

 

[Dave Weaver]

Or, simply:

my $count = 0;
$count++ while $something =~ /test/g;

Or save yourself the loop:

my $count = () = $something =~ /test/g;

 

[ced]

Or save yourself the loop:

my $count = () = $something =~ /test/g;

There's still a loop returning values which are just discarded
by the empty list of course. Losing the counter init./increm.
is very cool though.

 

[Anno Siegel]

Hi All,

My CPU taking 100% if I try to match more than the existing number of
specific matches in a string. Script is ...

my $something = "this is a test, just test, no kidding, small test, but
error in test. over over";
if ($something =~ m/((.*)test(.*)){5}/){
print "number of matches are 5, successful";
}
else{
print "no 5 matches, failure";
}

String "test" is repeated only 4 times in $something but if I am trying
to check whether the $something has 5, my CPU taking 100%. What is the
issue?

Probably excessive backtracking. Lots of alternatives have already been
proposed.

Anno