Data structures drive logic! (was Re3: Passing / evaluating / dieing on one line...)

[dragonchild]

Your example is spurious, because it's bad code.

my %Columns = (
    'label' => 0,
    'key' => 1,
    'cross' => 2,
);

foreach my $col_name (keys %Columns)
{
    $Columns[$col_name} = column_exists( \@data, $_[1] || $Columns{$co
+l_name} );
    die if $Columns{$col_name} == -1;
}

Now, adding a new column is a matter of changing the %Columns hash. In addition, it's much easier to factor out the %Columns hash to some configuration file this way than doing it your way.

In addition, this lends itself to even further improvements. For example, consider

my %Columns = (
    'label' => {
        default => 0,
        exists => 0,
    },
    'key' => {
        default => 1,
        exists => 0,
    },
    'cross' => {
        default => 2,
        exists => 0,
    },
);

foreach my $col_name (keys %Columns)
{
    $Columns[$col_name}{exists} =
        column_exists( \@data, $_[1] || $Columns{$col_name}{default} )
+;
    die if $Columns{$col_name}{exists} == -1;
}

THAT is self-documenting code!

Furthermore, any time I see

do_A; do_B; do_C;
do_D;
do_A; do_B; do_C;
do_E;
do_A; do_B; do_C;
do_C;

I was to do something like:

for (\&do_D, \&do_E, \&do_C) {
    do_A; do_B; do_C;
    $_->();
}

It's cleaner, more maintainable, and more extensible.

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