# Grammar from https://metacpan.org/pod/distribution/Marpa-R2/pod/Semantics.pod
:start ::= Expression
Expression ::= Number
  | '(' Expression ')' bgcolor => salmon
 || Expression '**' Expression bgcolor => red
 || Expression '*' Expression bgcolor => yellow color => black
  | Expression '/' Expression bgcolor => green color => orange
 || Expression '+' Expression bgcolor => blue color => orange
  | Expression '-' Expression bgcolor => cyan color => black

Number ~ [\d]+

:discard ~ whitespace
whitespace ~ [\s]+
10 + (6 - 1 / 3) * 2