Precedencia.eyp

%{
=head1 SYNOPSIS

Be sure Math::Tail in examples/Calculator/lib is reachable
compile it with 

  eyapp -C Precedencia.eyp 

execute the generated modulino with:

      ./Precedencia.pm -noslurp -c '2@3@4' -info  --margin 2

or:
      ./Precedencia.pm --debug --noslurp -c '2@3@4' -info  --margin 2

Try also with inputs:
   
    4@3@5
    4@3&5
    4&3@5
    4&3&5

The result will be the term describing the generated
Abstract Syntax Tree 

=head1 See also

    http://search.cpan.org/perldoc?Parse::Eyapp::debuggingtut

=cut

our $VERSION = '0.02';

%}

%token NUM = /\d+/
%left '@'
%right '&'  dummy

%tree bypass
%%
list
    : /* empty */
    | list '\n' {}
    | $list $e { print $e->str."\n"; 
                 $e->png(); 
                 $e; 
               }
    ;

e : %name NUM
      NUM
  | %name AMPERSAND
      e '&' e
  | %name AT
      e '@' e %prec dummy
  ;

%%

# We can explicit a lexer if we want:

__PACKAGE__->lexer(
    sub {
      my $parser = shift;
  
      for (${$parser->input()}) {    # contextualize
        m{\G(\s*)}gc;
        $parser->tokenline($1 =~ tr{\n}{});
  
        m{\G([0-9]+)}gc                and return ('NUM', $1);
  
        m{\G(.)}gc                     and return ($1,    $1);
  
        return('',undef);              # EOF
      }
    }
  );

# __PACKAGE__->main('Input (try st. like 2@3&4<CR><CTRL-D>): ') unless caller();

1;