challenge8.p6

# Challenge #1

#`[ Slow, naive, brute force perfect number calculation
sub is-perfect (Int $n) {
    ($n == sum grep $n %% *, 1 .. $n div 2) ??
      $n !!
      Empty
}
]

# Faster perfect number calculation
sub is-perfect (Int $n) {
    my $p = 2**$n - 1;
    $n.is-prime && $p.is-prime ??
    $p * 2**($n - 1)           !!
    Empty
}

# Returns in a reasonable time for up to ~15
.say for ( 1..* ).map( *.&is-perfect ).head(15);


# Challenge #2

# Pass in an optional width parameter to center the phrases within that width
sub center (*@strings, :$width) {
    my $pad = ceiling $width ??
      $width / 2             !!
      2 R/ chars max @strings, :by(*.chars);
    @strings.map( { ' ' x ($pad - .chars div 2) ~ $_ } ).join: "\n"
}

say center("This", "is", "a test of the", "center function");

my ($, $columns) = qx/stty size/.words;
say center("This", "is", "a test of the", "center function", :width($columns));