Algebraic data types: Difference between revisions

=={{Header|E}}==

=={{header|Perl 6}}==

{{works with|rakudo|2016.11}}

Perl 6 doesn't have algebraic data types (yet), but it does have pretty good pattern matching in multi signatures.

<lang perl6>enum RedBlack <R B>;

multi balance(B,[R,[R,$a,$x,$b],$y,$c],$z,$d) { [R,[B,$a,$x,$b],$y,[B,$c,$z,$d]] }

multi balance(B,[R,$a,$x,[R,$b,$y,$c]],$z,$d) { [R,[B,$a,$x,$b],$y,[B,$c,$z,$d]] }

multi balance(B,$a,$x,[R,[R,$b,$y,$c],$z,$d]) { [R,[B,$a,$x,$b],$y,[B,$c,$z,$d]] }

multi balance(B,$a,$x,[R,$b,$y,[R,$c,$z,$d]]) { [R,[B,$a,$x,$b],$y,[B,$c,$z,$d]] }

multi balance($col, $a, $x, $b) { [$col, $a, $x, $b] }

multi ins( $x, @s [$col, $a, $y, $b] ) {

when $x before $y { balance $col, ins($x, $a), $y, $b }

when $x after $y { balance $col, $a, $y, ins($x, $b) }

default { @s }

}

multi ins( $x, Any:U ) { [R, Any, $x, Any] }

multi insert( $x, $s ) {

[B, |ins($x,$s)[1..3]];

}

sub MAIN {

my $t = Any;

$t = insert($_, $t) for (1..10).pick(*);

say $t.gist;

}</lang>

This code uses generic comparison operators <tt>before</tt> and <tt>after</tt>, so it should work on any ordered type.

{{out}}

<pre>[B [B [B (Any) 1 [R (Any) 2 (Any)]] 3 [B (Any) 4 [R (Any) 5 (Any)]]] 6 [B [B (Any) 7 (Any)] 8 [B [R (Any) 9 (Any)] 10 (Any)]]]</pre>