On Feb 25, 2014, at 2:30 PM, Bill McCormick wrote:
> What would be the perl'ish way using map or some other sugar to check if a
> list of values meet some criteria? Instead of doing something like
>
> my @issues = qq(123,456,a45);
> my $max = 999;
>
> for (@issues) {
> die if $_ < 0 or $_ > $max;
> }
>
> I want to check if each list item is numeric and > 0 but less than $max.
>
> Cheers!
grep is the Perl function for testing a list of values against some criteria.
perldoc -f grep
'grep BLOCK LIST' will return all of the items in LIST that result in a true
value when BLOCK is evaluated. In scalar context, grep returns the number of
items that evaluated to true, so you can either save all of the true-ish items
or just get a count.
For example (untested):
my @fail = grep { $_ =~ /\D/ || $_ <= 0 || $_ >= $max } @issues;
Now @fail contains any member of @issues that fails any of the three tests:
1) contains a non-digit,
2) is less than or equal to zero,
3) greater than or equal to $max
If @fail is empty, everybody passed (that is, evaluated to false!)
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