> -----Original Message-----
> From: Robert Thompson [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, June 04, 2002 3:38 PM
> To: [EMAIL PROTECTED]
> Subject: Passing array to subroutine problem
>
>
> Hello,
>
> I have a subroutine where I want to pass some
> paramaters to it, but assign default ones if a paramater is
> not passed. This is similar to CGI.
>
> &mySub( -param1=>'my value', -param3=>'value' ); #
> -param2 would get a default value
>
>
> The problem I am running into is if one of the
> paramaters passed is an array, and the value passed is 0, the
> default value gets assigned instead of the 0 that was passed.
> Below is some code that shows what I am doing and how it breaks:
>
> #!/usr/bin/perl -Tw
>
> use strict;
>
> &Baz( one=>'all good', two=>['zero','one'] ); # text works
> &Baz( one=>'bad', two=>[0,1] ); # numbers fail
> &Baz( one=>'more bad', two=>['0','1'] ); # quoted numbers fail
>
>
> sub Baz {
> my %params = @_;
>
> $params{one} = "default" unless $params{one};
> $params{two}[0] = "default" unless $params{two}[0];
Comment this one out.
> $params{two}[1] = "default" unless $params{two}[1];
>
> # let's try some more, they still fail...
> $params{two}[0] = "default" unless defined($params{two}[0]);
This one works, but you need to comment out the one 3 lines up.
> $params{two}[0] = "default" unless $params{two}[0] ||
> $params{two}[0] == 0;
>
> print "one is $params{one}\n";
> print "two[0] is $params{two}[0]\n";
> print "two[1] is $params{two}[1]\n";
> print "\n";
>
> return(1);
> }
> __END__
If you want to have default values for arguments, you can use
the following trick:
sub foo
{
my %args = (arg1 => 'default1', arg2 => 'default2', @_);
...
}
The trick is to put your defaults first in the list, followed by @_. If
the same key appears more than once in a list assignment to a hash, only
the last value is used.
Now if you call foo(arg1 => 'bar'), the 'bar' will override 'default1'.
If you just call foo(), $args{arg1} will be 'default1'.
Make sense?
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