assume I had a Parse::RecDescent grammar that looked in part like this:

order: quantity color item
quantity: /\d+/
color: # what should this be?
item: 'pen' | 'pencil'

[download]

now assume in one script that uses this grammar, there was:

my @colors = ('red', 'green', 'blue');

[download]

while in another script there was:

my @colors = ('cyan', 'magenta', 'burnt umber');

[download]

How would I write the definition for color in the grammer so it would match only valid @colors? There may be many other scripts with different color combinations, and as the second example shows, they can be arbitrary strings with embedded spaces.

I suspect the answer involves having a function in each script like this:

sub is_valid_color
{
  my ($color) = @_;

  foreach (@colors)
  {
    return 1 if $color eq $_;
  }
  return undef;
}

[download]

but for some reason I just can't make the connection.

--
જલધર

In reply to Dynamic expansion of tokens with Parse::RecDescent by jaldhar

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