Re: [MacPerl] Problem with MacPerl 5.06

[wjm@metronet.com (Bill Middleton)]

On Feb 4,  7:13pm, Matthias Ulrich Neeracher wrote:
} Subject: Re: [MacPerl] Problem with MacPerl 5.06
} schinder@pjstoaster.pg.md.us (Paul Schinder) writes:
} >test.pl:
} >
} >#!/usr/local/bin/perl
} >package test;
} >
} >#$a = "test";
} >#my $a = "test";
} >local $a = "test";
} >
} >sub test {my $b = $a;return $b};
} >1;
} >
} >testmain.pl:
} >
} >#!/usr/local/bin/perl
} >
} >require "test.pl";
} >
} >$a = test::test();
} >print "$test::a, $a\n";
} >
} >Running testmain with the declaration line in test changed gives the following
} >
} >             MacPerl 5.06                     Sun Perl 5.001m
} >$a:            test, test                        test, test
} >local $a:          ,                                 ,
} >my $a:             ,                                 , test
} >
} >
} >The latter is what's been the problem with lwp5b6, because the authors
} >universally declare variables "my" outside of routines, and MacPerl
} >promptly forgets their existence and initial values.
} 
} As others have pointed out, it is not so clear whether what you're doing is
} really *supposed* to work. While conventional meaning of "lexical scoping"
} would imply that it does, the Perl manpages focus on my() being defined only
} for a single scope. However, the Perl5.0.2beta3 manpage gives an example which
} hints that this is possible.

I believe it should work in both versions.  Larry's intent with my was 
(at least partially) to emulate what the typical C programmer would expect.  
Witness:

 http://www.metronet.com/perlinfo/perl5/perl5.MY.lvalue.info

Since the variable $a is within the "containing block" of the package,
it should be visible to all subroutines within that package, _as long
as_ they dont declare their own version of $a.  

Here's a bit of C code to demonstrate the analogy.

int main(){
    int a = 1;  /* a is scoped to main */
    printf("a equals %d in main\n", a);
    foo(); bar(); baz();
}

int a  = 2;  /* redeclare a outside scope of main */

void foo(){
    printf("a equals %d in foo\n", a);  
}

void bar(){
    int a = 3;  /* redeclare a for bar only */
    printf("a equals %d in bar\n", a);
}
void baz(){
    printf("a equals %d again in baz\n", a);
}

Which prints:

a equals 1 in main
a equals 2 in foo
a equals 3 in bar
a equals 2 again in baz

And the equivalent perl code:

package test;
my $a = 2;
sub foo{print "a is $a in foo\n"}
sub bar{my $a = 3; print "a is $a in bar\n"}
sub baz{print "a is $a again in baz\n"}

package main;
my $a = 1;
print "a is $a in main\n";
test::foo(); test::bar(); test::baz();


} I'm not aware of having done any modifications to the standard perl source in
} this area either. I'll have to look further into this issue.
} 

I suspect Mac Bison.  But I'm Cc'ing this to perl5-porters, just in case
I've stuck my foot in my mouth again.

} Matthias
}-- End of excerpt from Matthias Ulrich Neeracher

Bill