How to calculate the number of match occurrences directly?

[Long Li]

Hi,
I want to calculate the number of match occurrences, for examples,

$string = "abcdabcd";
@a = $string =~ m/a/g;
$num_a = @a;

However, I do not want to use the array "@a" because I do not care
that array, espcially "$string" is very large and include many "a", I
just want to know the number of "a" occurrences. I tried

$num_a = $string =~ m/(a)/g;
or
$num_a = ( $string =~ m/a/g );

They both did not work. Please give me some suggestions, thanks.

 

[Anno Siegel]

Hi,
I want to calculate the number of match occurrences, for examples,

$string = "abcdabcd";
@a = $string =~ m/a/g;
$num_a = @a;

However, I do not want to use the array "@a" because I do not care
that array, espcially "$string" is very large and include many "a", I
just want to know the number of "a" occurrences. I tried

$num_a = $string =~ m/(a)/g;
or
$num_a = ( $string =~ m/a/g );

They both did not work. Please give me some suggestions, thanks.

There's a trick to that:

$num = () = /a/g;

The "()" provide list context to the regex, but the actual variable
(a scalar) is assigned the number of elements. Capturing parentheses
are not necessary.

If you only ever want to count single characters, tr/// is simpler
and more efficient:

$num = tr/a//;

Anno

 

[Gunnar Hjalmarsson]

I want to calculate the number of match occurrences, for examples,

$string = "abcdabcd";
@a = $string =~ m/a/g;
$num_a = @a;

However, I do not want to use the array "@a" because I do not care
that array, espcially "$string" is very large and include many "a",
I just want to know the number of "a" occurrences. I tried

$num_a = $string =~ m/(a)/g;
or
$num_a = ( $string =~ m/a/g );

They both did not work. Please give me some suggestions, thanks.

You are asking a FAQ.

perldoc -q count

Please consult the FAQ, thanks.