views:

83

answers:

2

Best asked by an example:

my $var1=1;
my $var2;
my $var3=3;

# say "at least one undef" if at least one of $var1, $var2, $var3 is undef

Obviously I can explicitly loop and do that, but I always like to find one liners that achieve the same result.

+10  A: 
if (grep { !defined } $var1, $var2, $var3) {
  say 'at least one undef'
}

one liner

say 'at least one undef' if grep { !defined } $var1, $var2, $var3;
Bob
What about that cool `//` operator? Isn't it of use here?
David B
`//` is a short-circuit operator, so it would be useful if you had a code path you want to execute conditionally based on the definedness of a single value. I can't think of a use here, but TMTOWTDI.
Bob
@David B, `//` is defined-or, so it can only be used to calculate "at least one defined". To get "at least one undef", you'd need a defined-and operator, which doesn't (currently) exist.
cjm
+1  A: 

expanding on Bob's answer, in some cases, you might want to grab the actual count

say 'has ', scalar ( grep { not defined } $var1,$var2,$var3 ),' undef';
erickb