SAMS Teach Yourself Perl in 24 Hours THIRD EDITION

Building a Module

To understand how a module is put together, let's walk through a simple example: a small statistics library. This will re-use functions from the end of Hour 8, abbreviated for space. The sample module, which we're going to call TYPStats, is shown in Listing 17.1.

Listing 17.1. Statistics Module

1: #!/usr/bin/perl -w 2: use strict; 3: package TYPStats; 4: 5: sub mean { 6: my(@data) = @_; 7: my $sum; 8: $sum += $_ foreach(@data); 9: return @data ? ($sum / @data) : 0; 10: } 11: sub median { 12: my(@data)=sort { $a <=> $b} @_; 13: if (scalar(@data) % 2) { 14: return($data[@data / 2]); 15: } 16: return(mean($data[@data / 2], 17: $data[@data / 2 - 1])); 18: } 19: 1;

This should be saved into a file called TYPStats.pm in the same ...