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Re^3: Context aware functions - best practices?

by LAI (Hermit)
on Jan 14, 2003 at 21:50 UTC ( #226971=note: print w/replies, xml ) Need Help??

in reply to Re^2: Context aware functions - best practices?
in thread Context aware functions - best practices?

You are aware that
scalar (@x = foo(1,2,3,5));
will evaluate to the number of elements returned by foo rather than return the last one of them, right? :)

Yes, of course. I wrote that in reference to my $x = foo(1); setting $x to 1 :oP

I agree that it would be a rare case when the flattened array would be an acceptable return value, but I still don't like the idea of throwing away data. Oh, well. The only alternative I can think of is the hideous

return wantarray ? @arr : $#arr ? \@arr : $arr[0];

which borders on the obfuscated. I wouldn't use something like that if I were you. Of course I'm me, and love using lines like that, but I digress...

Zaxo's suggestion of using $arr[-1] makes sense too, especially if the sub is doing something cumulative with its args. Imagine a sum() function that keeps track of all the intermediate sums, or whatever.


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Re^4: Context aware functions - best practices?
by Aristotle (Chancellor) on Jan 14, 2003 at 23:32 UTC

    Ugh, that's the worst of both worlds, esp if I didn't know the number of return values beforehand (I do in the situation at hand). In that case every invocation in scalar context will have to be tested with ref.. if it at least consistently returned an arrayref I wouldn't have to think about it.

    As I said, what I want is the same convenience as CGI offers with my $foo = $cgi->param(''); vs my ($foo) = $cgi->param(''); - you get the same result either way. Nothing else.

    If you don't like the idea of throwing away results, consider my $foo = (bar(), baz(), qux());. I'm asking for pretty much the same semantics.

    Makeshifts last the longest.

      Ugh, that's the worst of both worlds

      Hurrah for nauseatingly ugly code...

      Anyway, yeah. The return type would definitely have to be the same regardless of the args. Having to test the type every time a sub is called is unacceptable. How does CGI's $calar = $cgi->param() decide which value to return, though (if it's a multivalue parameter)? Is it just the first (or last) one input?

      I just RTFM'd and RTFSource'd, and CGI->param() does this:

      return unless defined($name) && $self->{$name}; return wantarray ? @{$self->{$name}} : $self->{$name}->[0];

      There you have it, I guess. Return the whole array or the first element. I still like Zaxo's idea of returning @rray[-1], though... I guess it depends what sub foo does.


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