RE: purge: opposite of grep

[David Whipp]

 Miko O'Sullivan [mailto:[EMAIL PROTECTED]] wrote:
> SUMMARY
> 
> Proposal for the "purge" command as the opposite of "grep" in 
> the same way that "unless" is the opposite of "if".

I like it.

But reading it reminded me of another common thing I do
with grep: partitioning a list into equivalence classes.

a simple case:
  @pass = grep {$_->ok} @candidates;
  @fail = grep {! $_->ok} @candidates;

This could perhaps be expessed as:

  (@pass, @fail) = unzip { $_->ok } @candidates;

A more general mechanism might be:

  %results = partition
      { $_->pass ? "pass" : $_->fail ? "fail" : "unknown" }
      @canditates;

  print "pass: @{%results{pass}}";
  print "fail: @{%results{fail}}";
  print "unknown: @{%results{unknown}}";


Dave.