parse.p6

#!/usr/bin/env perl6

# use Grammar::Tracer;
# use Grammar::Debugger;

grammar Offsides {
  token TOP {
    <tree>*
  }

  token tree {
    $<indent>=(\s*) <text>

    <subtree(~$<indent>)>*
  }

  token subtree($current-indent) {

    $current-indent $<more-indent>=(\s+) <text>

    # If I comment this line out, $<more-indent> doesn't
    # get passed into the subtree!
    { say "more-indent: [{ $<more-indent> }]" }

    # Might have some sub-trees with more indent
    <subtree($current-indent ~ ~$<more-indent>)>*
  }

  token text {
    \S .*? $$
  }
}

my $test-input = "hello
    this is
        a
    test to see
    if this
          can calculate
          the offside
    rule";

my $match = Offsides.parse($test-input);
# say $match;

# use LREP;
# LREP::here;

sub print-trees($trees, $current-indent = 0) {
  for $trees.flat -> $tree {
    say ("  " x $current-indent) ~ "[{ $tree<text> }]";
    # say "indent: $current-indent";
    # say "text: $tree<text>";
    print-trees($tree<subtree>, $current-indent + 1);
  }
}

print-trees($match<tree>);

result.txt

Use of Nil in string context  in regex tree at ./parse.p6:11
more-indent: [
    ]
more-indent: [    ]
Use of Nil in string context  in regex tree at ./parse.p6:11
more-indent: [
    ]
Use of Nil in string context  in regex tree at ./parse.p6:11
more-indent: [
    ]
more-indent: [      ]
more-indent: [      ]
Use of Nil in string context  in regex tree at ./parse.p6:11
more-indent: [
    ]
Use of Nil in string context  in regex tree at ./parse.p6:11
[hello]
  [this is]
    [a]
  [test to see]
  [if this]
    [can calculate]
    [the offside]
  [rule]