algebra.p6

grammar Algebra {
    rule TOP { ^^ <expression> $$ }
    rule expression { <+symbol+sum+product> }

    rule sum {
        | <symbol>\+<expression>
    }
    rule product {
        | <symbol>\*<symbol>
        | <symbol>\*\(<sum>\)
        | \(<sum>\)\*<symbol>
        | <product>\*<symbol>
    }

    token symbol { <ident> | <number> }
    token number { <.integer><.fraction>? }
    token fraction { \.<.digit>+ }
    token integer { <[+-]>? 0 | <[1..9]><.digit>* }
}

use Test;
plan *;

ok Algebra.parse($_), $_ for
<1 12 2 pi 1+2 1+2+3 2*2 3*(2+1)
(1+1)*2
(1+1)*2*3
>;

# vim: ft=perl6