gistfile1.pl

sub sample3 {
    my ( $a, $b, $c, $d ) = @_;

    if ( $a && $b && !$c && !$d) {
        return "a and b";
    }
    if ( $a && !$b && $c && !$d) {
        return "a and c";
    }
    if ( $a && !$b && !$c && $d) {
        return "a and d";
    }
    if ( !$a && $b && $c && !$d) {
        return "b and c";
    }
    if ( !$a && $b && !$c && $d) {
        return "b and d";
    }
    if ( !$a && !$b && $c && $d) {
        return "c and d";
    }
    return $a+$b+$c+$d;

}


sub bit2name{
    my @bits  = @_;
    my @names = qw/a b c d/;
    my $count = 0;

    return grep{$_} map{
       $count++;
       $_ ? $names[$count-1] : undef;
    } @bits
}


use List::Util qw/sum/;
sub answer3{
    my ( @bits ) = @_;
    my $sum = sum @bits;
    return $sum unless $sum == 2;
    return join " and ",bit2name(@bits);
}

sub check_bool_eq {
    my ( $num, $func_a, $func_b ) = @_;
    for my $s ( 1 .. 2**$num ) {
        my @args = map { ($s & ( 1 << $_ ))? 1: 0 } ( 1 .. $num );
        is( $func_a->(@args), $func_b->(@args) );

    }
}

check_bool_eq( 4, \&sample3, \&answer3 );