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Re: Use method/function signatures with Perl

by radiantmatrix (Parson)
on Dec 06, 2004 at 17:09 UTC ( #412698=note: print w/replies, xml ) Need Help??

in reply to Use method/function signatures with Perl

This is kind of cool, but I've been severely bitten by source filters in the past, and continue to have a number of personal stylistic issues with using them. What I'd like to see (and if someone knows of a CPAN module that does this, I'd be grateful) is something that would allow subs to be written thusly:

use Verifier; my $verify = new Verifier (on_failure => sub { die(join (',',@_)) }) sub foobar { ## The '-' in front of hashref means $bar is an optional paramater my ($foo, $bar) = $verify->type ( \@_, qw/scalar -hashref/); print "Using $foo:\n"; return $foo unless %$bar; for (keys %$bar) { print "$_ => $$bar{$_}\n" } return $$bar{'result'}; }

That is, I'd really like to see verification of parameter types handled by a verifier object rather than by a source filter. Yes, I know it's not quite the same thing; but by eval'ing the type verifier call, one could achieve the same basic functionality.

Update: It turns out, thanks to a mention by dragonchild and xdg, that Params::Validate does just the above. An example of the above code, but using that CPAN module, can be found a bit further down in this discussion.

require General::Disclaimer;
s//2fde04abe76c036c9074586c1/; while(m/(.)/g){print substr(' ,JPacehklnorstu',hex($1),1)}

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Re^2: Use method/function signatures with Perl
by dragonchild (Archbishop) on Dec 06, 2004 at 17:10 UTC
    What's wrong with how Params::Validate does things?

    Being right, does not endow the right to be rude; politeness costs nothing.
    Being unknowing, is not the same as being stupid.
    Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence.
    Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.

      Aha. I knew someone must have had the same general idea before! Thank you for that link. I only have a tiny gripe with it vs. my ideal verifier, which is that Params::Validate only validates, where as what I wrote above would imply validation and returning of the validated parameters (rolling two operations into one).

      I'm certainly not about to reinvent a wheel over something so minor, though. The module you recommended will work nicely. Thanks again!

      Update: this is what I get for merely scanning the POD before posting. As xdg points out, Params::Validate does everything I have wished for:

      use Params::Validate; sub foobar { my ($foo, $bar) = validate_pos ( @_, {type = SCALAR, regex=>/.+/}, {type = HASH_REF} ); print "Using $foo:\n"; return $foo unless %$bar; for (keys %$bar) { print "$_ => $$bar{$_}\n" } return $$bar{'result'}; }

      is equivalent to my earlier code.

      require General::Disclaimer;
      s//2fde04abe76c036c9074586c1/; while(m/(.)/g){print substr(' ,JPacehklnorstu',hex($1),1)}

        I think if you read the POD closely, you'll see Params::Validate does what you want. E.g. (from the POD,

        my @p = validate( @_, 1, { default => 99 } );

        You can also set a global on_fail callback to die however you want.


        Code posted by xdg on PerlMonks is public domain. It has no warranties, express or implied. Posted code may not have been tested. Use at your own risk.

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