Tree from nesting levels: Difference between revisions

===String Eval===

{{trans|Perl}}

<lang perl6>use MONKEY-SEE-NO-EVAL;

sub to_tree_string_eval ( @xs --> Array ) {

my @gap = [ |@xs, 0 ] Z- [ 0, |@xs ];

my @open = @gap.map( '[' x * );

my @close = @gap.map( ']' x -* );

my @wrapped = [Z~] @open, @xs, @close.skip;

return EVAL @wrapped.join(',').subst(:g, ']]', '],]') || '[]';

}

my @tests = (), (1, 2, 4), (3, 1, 3, 1), (1, 2, 3, 1), (3, 2, 1, 3), (3, 3, 3, 1, 1, 3, 3, 3);

say .Str.fmt( '%15s => ' ), .&to_tree_string_eval for @tests;</lang>

{{out}}

<pre>

=> []

1 2 4 => [1 [2 [[4]]]]

3 1 3 1 => [[[3]] 1 [[3]] 1]

1 2 3 1 => [1 [2 [3]] 1]

3 2 1 3 => [[[3] 2] 1 [[3]]]

3 3 3 1 1 3 3 3 => [[[3 3 3]] 1 1 [[3 3 3]]]

</pre>