RE: Safe list assignment

Chas. Owens wrote:

>>safe_assign ($a, $b, $c) = @array;    # will die if scalar(@array) != 3
>
>Not that I am aware of, but it is a breeze to build one:

[code snipped]

That doesn't quite work - try testing it with

    my @a = (1 .. 3);
    my ($a, $b, $c);
    safe_assign [ $a, $b, $c ], @a;
    say foreach $a, $b, $c;

You'd need to make a version taking references, so it would look like

    safe_assign_b [ \($a, $b, $c) ], @a;

or alternatively, write a version that modifies its parameters directly and takes the RHS as a list reference:

    sub safe_assign_c {
        croak 'usage: safe_assign_c LHS, ..., RHS-listref' if @_ < 2;
        my @rhs = @{pop @_};
        croak 'wrong number of elements in RHS' if @_ != @rhs;
        foreach (@_) {
            $_ = shift @rhs;
        }
    }
    my @a = (1 .. 3);
    my ($a, $b, $c);
    safe_assign_c $a, $b, $c, \@a;
    say foreach $a, $b, $c;

And then this sort of thing could be generalized somehow to make safe versions of assignments like

    my ($first, $second, @rest) = @a;

where clearly @a should have two or more elements.

But my question is, is there a standard way to do this?  Like a CPAN module that provides a concise and clear syntax to do safe list assignments.  It seems like it should be a pretty common operation.  Ideally, 'use warnings' would give a runtime warning when the LHS and RHS don't match up.

If there isn't a consensus on the recommended way to do this (in the same way that Carp is the recommended way to give error messages, File::Slurp is the recommended way to read a whole file, etc) then I may try to make one.

-- 
Ed Avis <[email protected]> 

______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email 
______________________________________________________________________