in reply to Re^2: Perl scoping not logical...?
in thread Perl scoping not logical...?

Does that make sense?

Not really.

I certainly don't want the routine *compiled* each time I invoke the routine. I want it to use the same lexical frame as the variables that the sub is defined in.

You can either pass them in to the sub, or you can use lambdas. In perl, today, you can't have it both ways. Even if you had named lexical subs, they'd still have to be recompiled each time (minus compiler optimizations, which may exist for function ref lambdas). Anyway, I think function refs are perfectly clear. They're very widely used and when you need a lambda, they're the appropriate way to do it.

Here's just a couple of the common uses. You can think of millions more I'm sure. Don't shy away from function refs. They're quite clear.

my $awesome = awesome(); print "still tickin'\n" while $awesome->(); sub awesome { my @a = (1 .. 10); return sub { shift @a }; } my %code_table = ( action1 => sub {print "doin' it\n"}, ); $code_table{action1}->(); # also awesome

People really expect the subs to work they way they do now though, so it's not likely to be changed until perl6 at the earliest. Imagine how much code would break if they suddenly worked differently?

The locals aren't really being crushed...their just in flux....(duplicated, really)....

Oh, I get it. I'm just saying that...

my ($c,$d); my ($c,d) = (4,5); # ...maybe we can live without the fi +rst my?

Essentially, I was asking if that was unintentional and might be causing your troubles.

-Paul

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Re^4: Perl scoping not logical...?
by perl-diddler (Chaplain) on May 01, 2008 at 01:50 UTC
    People really expect the subs to work they way they do now though, so it's not likely to be changed until perl6 at the earliest. Imagine how much code would break if they suddenly worked differently?
    I don't believe I am suggesting that existing "subs" work differently. What I proposed was the ability to declare a sub with "my" just as one does with variables. Do you think that if people saw:
    sub print_sum($$) { my ($x, $y) =@_; my sub adder {return $_[0]+$_[1] }; printf "sum of $x, $y = %d\n", adder($x, $y); }
    That people would get confused about why "adder" would be used as a helper function to the main sub "print_sum"?

    Is there another possible meaning of "my sub" that would be confused with using it to specify that sub is local to the block just like the variables are?

    I'm not entirely clear about the term 'lambda'. Something to do with anonymous functions in lisp? I don't recall seeing it in the perl docs I've read (doesn't me an it's not there...just don't recall it! :-)).

      You are far from the first to want lexical subroutines. There's a source-filter using proof-of-concept in Sub::Lexical. I don't recall there being any objection to actually implementing them in perl5 - it just hasn't happened to date (and may never, since it would be a lot of work and offer limited benefit over just using a lexical coderef).