Welcome back to the monastery Xiong. You must be exhausted after your long pilgrimage away from here. Sit down; take the weight off your feet; have a tankard of this year's brew.

Overall, I think your rewrite is an improvement of the original script. However, I think the else block which can never be reached may serve to confuse future readers of your scripture.

Also, I note that in the cases where $cf is false, you don't check that $unit is defined. Obviously I don't know the context where this code appears. Perhaps it is guaranteed to be defined. But if not, that's a case that should probably be covered. Doing the definedness check twice (within both blocks where $cf is false) violates DRY, so this could be done upfront.

# Four-outcome tree
my $cf      = !!$code;
my $af      = !!( $args and ref $args );

$cf or defined($unit) or die('$unit not defined');

if    (  $cf &&  $af ) {
    @ARGV       = @$args;
} 
elsif (  $cf && !$af ) {
    @args       = ();
} 
elsif ( !$cf &&  $af ) {
    @args       = @$args;
    $code       = $unit . q{(@args)};
} 
elsif ( !$cf && !$af ) {
    @args       = ();
    $code       = $unit . q{()};
}

[download]

Alternatively, you could use an assertion module (I keep meaning to release PerlX::Assert as a stand-alone module), which would allow:

# Four-outcome tree
my $cf      = !!$code;
my $af      = !!( $args and ref $args );
if    (  $cf &&  $af ) {
    @ARGV       = @$args;
} 
elsif (  $cf && !$af ) {
    @args       = ();
} 
elsif ( !$cf &&  $af ) {
    assert defined($unit);
    @args       = @$args;
    $code       = $unit . q{(@args)};
} 
elsif ( !$cf && !$af ) {
    assert defined($unit);
    @args       = ();
    $code       = $unit . q{()};
}

[download]

... which of course does include some repetition, but it's such a small amount of code that is repeated, it doesn't seem worth worrying about.

use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

In reply to Re: Case Exhaustion Tree by tobyink
in thread Case Exhaustion Tree by Xiong

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