Editing Raku (programming language) (section)

===Junctions===
Raku introduces the concept of ''junctions'': values that are composites of other values.<ref name="syn9"/> In their simplest form, junctions are created by combining a set of values with junctive [[Operator (programming)|operator]]s:
<syntaxhighlight lang="raku">
# Example for | ("any") Junction:
my $color = 'white';
unless $color eq 'white' | 'black' | 'gray' | 'grey' {
    die "Color printing not supported\n";
}

# Example for & ("all") Junction:
my $password = 'secret!123';
if $password ~~ /<:alpha>/ & /<:digit>/ & /<:punct>/ {
    say "Your password is reasonably secure";
}
</syntaxhighlight>
<code>|</code> indicates a value which is equal to either its left- ''or'' right-hand arguments. <code>&</code> indicates a value which is equal to both its left- ''and'' right-hand arguments. These values can be used in any code that would use a normal value. Operations performed on a junction act on all members of the junction equally, and combine according to the junctive operator. So, <code>("apple"|"banana") ~ "s"</code> would yield <code>"apples"|"bananas"</code>. In comparisons, junctions return a single true or false result for the comparison. "<code>any</code>" junctions return true if the comparison is true for any one of the elements of the junction. "<code>all</code>" junctions return true if the comparison is true for all of the elements of the junction.

Junctions can also be used to more richly augment the type system by introducing a style of [[generic programming]] that is constrained to junctions of types:
<syntaxhighlight lang="raku">
subset Color of Any where RGB_Color | CMYK_Color;
sub get_tint(Color $color, Num $opacity) {
    ...
}
</syntaxhighlight>