use Perl

• Useful? Dunno (Score:1)

  by ferreira (5993) on 2007.08.14 13:27 (#56974) Homepage Journal

  But amusing and too easy to write down. Well, my first implementation only did the scalar context case. The second left me hanging between a do-it-all implementation which was not very clear to read and another with auxiliary methods can_oneof and can_someof. The third implementation prevented me of using my @a; for ( @_ ) { ...; push @a, ... }; return @a instead of a proper map. This is it.

  package USUAL;
  
  sub can_any {
      return wantarray ? goto &can_someof : goto &can_oneof;
  }
  
  sub can_oneof {
      my $self = shift;
      for ( @_ ) {
          my $can = $self->can($_);
          return $can if $can;
      }
      return;
  }
  
  sub can_someof {
      my $self = shift;
      return map { $self->can($_) // () } @_;
  }
  
  1;

  Now insert USUAL into the @ISA array of the package to which belongs the object you are querying about. Yes, I resisted the sin of adding those methods into UNIVERSAL.

  This asymmetrical implementation with a for for the scalar case and a map for the list context made me want a method which did the map job but got rid of the undefs and a scalar equivalent which returned the first defined result value. I reread the docs of List::Util and List::MoreUtils but they did not help me.

  With such methods, the implementation above would look like:

  sub can_oneof {
      my $self = shift;
      return first_defined_value { $self->can($_) } @_;
  }
  
  sub can_someof {
      my $self = shift;
      return defined_values { $self->can($_) } @_;
  }

  Now that's much more functional-stylish.

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