NumSeq::Iter - Generate a coderef iterator from a number sequence specification (e.g. '1,3,5,...,101')


This document describes version 0.005 of NumSeq::Iter (from Perl distribution NumSeq-Iter), released on 2022-01-21.


  use NumSeq::Iter qw(numseq_parse numseq_iter);

  my $iter = numseq_iter('1,3,5,...,13');
  while (my $val = $iter->()) { ... } # 1,3,5,7,9,11,13

  $iter = numseq_iter('1,3,5,...,10');
  while (my $val = $iter->()) { ... } # 1,3,5,7,9

  my $res = numseq_parse('');             # [400, "Parse fail: Please specify one or more number in number sequence: ''"]
  my $res = numseq_parse('1,5,2');        # [200, "OK", {numbers=>[1,5,2], has_ellipsis=>0, type=>'itemized', inc=>undef}]
  my $res = numseq_parse('1,2,3');        # [200, "OK", {numbers=>[1,2,3], has_ellipsis=>0, type=>'itemized', inc=>undef}]
  my $res = numseq_parse('1,2,3,...');    # [200, "OK", {numbers=>[1,2,3], has_ellipsis=>1, type=>'arithmetic', inc=>1, last_number=>undef}]
  my $res = numseq_parse('1,3,9,...');    # [200, "OK", {numbers=>[1,3,9], has_ellipsis=>1, type=>'geometric',  inc=>3, last_number=>undef}]
  my $res = numseq_parse('1,3,5,...,13'); # [200, "OK", {numbers=>[1,3,5], has_ellipsis=>1, type=>'arithmetic', inc=>2, last_number=>13}]
  my $res = numseq_parse('2,3,5,...');    # [400, "Parse fail: Can't determine the pattern from number sequence: 2, 3, 5"]


This module provides a simple (coderef) iterator which you can call repeatedly to get numbers specified in a number sequence specification (string). When the numbers are exhausted, the coderef will return undef. No class/object involved.

A number sequence is a comma-separated list of numbers (either integer like 1, -2 or decimal number like 1.3, -100.70) with at least one number. It can contain an ellipsis (e.g. '1,2,3,...' or '1, 3, 5, ..., 10').

When the sequence has an ellipsis, there must be at least three numbers before the ellipsis. There can optionally be another number after the ellipsis to make the sequence finite; but the last number can also be Inf, +Inf, or -Inf. Currently only simple arithmetic sequence ('1,3,5') or simple geometric sequence ('2,6,18') is recognized.




 $iter = numseq_iter([ \%opts ], $spec); # coderef



 my $res = numseq_parse([ \%opts ], $spec); # enveloped response

See "numseq_iter" for list of known options.


Please visit the project's homepage at


Source repository is at


Other iterators: IntRange::Iter, Range::Iter

CLI for this module: seq-numseq (from App::seq::numseq). There's another CLI named numseq (from App::numseq), but it is only tangentially related.


Raku's lazy lists.


perlancar <>


To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

 % prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla plugin and/or Pod::Weaver::Plugin. Any additional steps required beyond that are considered a bug and can be reported to me.


This software is copyright (c) 2022, 2021 by perlancar <>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.