Using overload to parse arithmetic terms

[esskar]

hi,

i wrote a package Foo::Expression::Arithmetic, a package Foo::Number and a package Foo::Variable. I used overload to be able to do the following:

my $x1 = Foo::Number->new()->value( 10 );
my $x2 = Foo::Number->new()->value( 20 );
my $x3 = Foo::Number->new()->value( 30 );
my $x4 = Foo::Number->new()->value( 40 );

my $v1 = Foo::Variable->new()->name( 'a' )->value( 50 );

my $c1 = $v1 - $x1 + $x2 + $x3 - $x4;
my $c2 = $c1 * $v1;

$c1 and $c2 are now objects of type Foo::Expression::Arithmetic. Foo::Expression::Arithmetic has a output function, so outputing $c1 and $c2 gives me the following:

a - 10 + 20 + 30 - 40      # $c1
a - 10 + 20 + 30 - 40 * a  # $c2

Now i want to be able to do the following:

my $c3 = ( $x1 + $x2 ) * $v1;

not achieve the following output:

( 10 + 20 ) * a   # $c3

use overload 
  '(' => \&left_parenthesis,    
  ')' => \&right_parenthesis,

is not working. :-( Any ideas?

2006-02-07 Retitled by Arunbear, as per Monastery guidelines
Original title: 'overload'