Beefy Boxes and Bandwidth Generously Provided by pair Networks
There's more than one way to do things

Leading empty array elements after splitting

by Anonymous Monk
on Aug 22, 2016 at 15:16 UTC ( [id://1170175]=perlquestion: print w/replies, xml ) Need Help??

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I'm attempting to extract numbers from codes in this generalised format (always begin with MD:Z: but what follows is variable):


Desired output (separate array elements):

4 3 7 0 2 9 44

As I need to maintain positional information and length of each number (i.e. it must be clear that 44 = 44 and not the product of something like 4T4 after screening out letters) i've tried to use split:

my @test = split((/\D/g), $input);

To split on any non-number; however this returns a set of leading empty array values arising from the consecutive matches on 'MD:Z:'. Is there a way to suppress these or a better way to go about getting the desired result?

Replies are listed 'Best First'.
Re: Leading empty array elements after splitting
by Athanasius (Archbishop) on Aug 22, 2016 at 15:26 UTC

    If you use warnings, you’ll see that the /g modifier on the regex has no effect within a split. But why not keep the modifier, change \D to \d+, and dispense with split altogether?

    1:22 >perl -MData::Dump -wE "my $input = 'MD:Z:4C3C7C0T2^T9C44'; my @ +test = $input =~ /\d+/g; dd \@test;" [4, 3, 7, 0, 2, 9, 44] 1:22 >

    Hope that helps,

    Athanasius <°(((><contra mundum Iustus alius egestas vitae, eros Piratica,

      use warnings; use strict; Are always on for me - no warning was given, odd!

        What version of Perl are you using (perl -v)?

        On both 5.20.3 and 5.24.0, this code produces the following warning:

        perl -wMstrict -E 'my @test = split((/\D/g), "x4d77");' Use of /g modifier is meaningless in split at -e line 1.
Re: Leading empty array elements after splitting
by stevieb (Canon) on Aug 22, 2016 at 15:27 UTC

    I'd use a global regex to extract just the digits directly into an array:

    use warnings; use strict; my $string = 'MD:Z:4C3C7C0T2^T9C44'; my @nums = $string =~ /\d+/g; print "$_\n" for @nums;


    4 3 7 0 2 9 44
Re: Leading empty array elements after splitting
by TomDLux (Vicar) on Aug 23, 2016 at 16:01 UTC

    Extracting just the numbers works well, but since you describe a problem with getting blank stuff you don't want, you might as well know about grep ...

    22 11:56:12 tomdlux [ ~ ] $ p522 -E 'say for split /\D+/, "MD:Z:4C3C7C0T2^T9C44"' + 4 3 7 0 2 9 44 23 11:56:19 tomdlux [ ~ ] $ p522 -E 'say for grep {length $_} split /\D+/, "MD:Z:4C3C7C0T2^T9C44 +"' 4 3 7 0 2 9 44

    As Occam said: Entia non sunt multiplicanda praeter necessitatem.

Log In?

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: perlquestion [id://1170175]
Approved by Athanasius
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others admiring the Monastery: (4)
As of 2024-04-14 14:11 GMT
Find Nodes?
    Voting Booth?

    No recent polls found