Chris,

You can examining the return value from a function by examining it's
'context'. List context is indicated by a true return value. If it returns a
value that is false but defined, then the function's return value will be
used in scalar context. If it returns undef, it isn't being asked to provide
a value at all.

if (myFunction()) {
    print "In list context\n";
    return @many_things;
} elsif (defined myFunction()) {
    print "In scalar context\n";
    return $one_thing;
} else {
    print "In void context\n";
    return;  # nothing
}

mysub();                    # void context

$a = mysub();               # scalar context
if (mysub()) {  }           # scalar context

@a = mysub();               # list context
print mysub();              # list context

Regards,

Piers

-----Original Message-----
From: Chris Ralph [mailto:webmaster@g...]
Sent: 17 November 2002 04:57
To: Pro_Perl
Subject: [pro_perl] Determine context


Hi,
Does anyone know how to tell if a return value from a function should be
scalar or other context ?

Example:

sub foobar
{
# Code here

if ( scalar_was_requested ){
return $scalar;
}elsif ( array_was_requested){
return @array;
}else{
return "error";
}
}

Now I call the function, and either an array or scalar should be returned,
depending on the context:

$val = foobar; # return scalar
@vals = foobar; # return array

What I can't work out is how to tell which variable type was requested..
I know a lot of built-in functions do this, but how do I go about
producing this behaviour in user defined functions ?

Chris