Answer: How to deal with undefined returned variables.


Perl: the Markov chain saw
	PerlMonks

Answer: How to deal with undefined returned variables.

by Russ (Deacon)

on Mar 05, 2002 at 19:51 UTC ( #149483=categorized answer: print w/replies, xml )

Need Help??

Q&A > subroutines > How to deal with undefined returned variables. - Answer contributed by Russ

knight makes a good point. Fortunately, in Perl 6, there will be a defaulting operator to simplify this very problem.

A binary // operator is the defaulting operator.
That is:
$a // $b
[download]
is short for:
defined($a) ?? $a :: $b
[download]
except that the left side is evaluated only once. It will work on arrays and hashes as well as scalars. It also has a corresponding assignment operator, which only does the assignment if the left side is undefined:
$pi //= 3;
[download]

Perl 6 should be such fun!

Comment on Answer: How to deal with undefined returned variables. Select or Download Code

Replies are listed 'Best First'.
Re: Answer: How to deal with undefined returned variables. by rinceWind (Monsignor) on Mar 06, 2002 at 17:00 UTC
I take it that the difference between // and \|\| is the difference between testing truthfulness and testing definedness. Hence there is not difference between $a // $b and $a \|\| $b unless $a is 0 or "". It doesn't sound that useful to me.	[reply]

Chatterbox^?

How do I use this? | Other CB clients

Other Users^?

Others making s'mores by the fire in the courtyard of the Monastery: (5)

As of 2017-08-16 18:42 GMT

Sections^?

Information^?

Find Nodes^?

Leftovers^?

Voting Booth^?

Notices^?