For me at present, at worst a closure does the job of a static variable, at best it can be likened to a very simple object1. 

sub function_called {
    my $calls = 0;

    return { return ++$callS }
}

[download]
or

A larger closure to enable a generic SQL template maker and deployer. 

sub late_bound_sql {

    my $string = join ('',@_); # collate args into SQL statement.
    my $late_bound_fields = m/ \? /g; # Count late bound fields.
    my $sql = $dbh->prepare($string); # Create sql template.
    
    return sub {
        return 0 if $#_ != $late_bound_fields;  # bad param count.

        for (0..$#_) {  # For each argument, assume in sequence.
            $sql->bind_param($_, $_[$_]); # Apply bind param.
        }

        if ($sql->execute()) { # Do _this_ sql.
            return 1;
        }
        else {
            return 0;
        }    
    }
}

# Create closures.
$lb1 = late_bound("INSERT INTO foo VALUES ( x = ?, y = ?) ");
$lb2 = late_bound("INSERT INTO bar, VALUES (a = ?, b = NULL)");

# Use them.
&$lb1(2,4);  # Inserts x= 2, y= 4 to table foo.
&$lb2("cuttlefish");  # Inserts a= cuttlefish, b= NULL to table bar

[download]
I make no claims as to the accuracy of this code, it's a variation, of one I did a while ago, without nice validation or passing, but enough I hope to clarify what I meant ;-)

--
Brother Frankus.

In reply to Re: Why Closures? by frankus
in thread Why Closures? by mothra

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