Higher-Order Parsing

Labeled blocks

Lately my big project has been a constraint-oriented drawing system called linogram
The input language contains constructions like:

        constraints { ... }

And:

        define square extends rectangle { ... }

So I use an even higher-level parser constructor:

        sub labeled_block {
          my ($header, $item, $separator) = @_;
          $separator = lookfor(";") unless defined $separator;
          conc($header, 
               lookfor("{"), 
               list_of($item, $separator),
               lookfor("}"));
        }

And define really complex parsers with it:

        $constraint_block = 
          labeled_block(L("CONSTRAINTS"), $constraint);

        $definition = 
          labeled_block($Definition_header, $declaration);