:default       ::= action => [name, value]

lexeme default = action => [name,value] latm => 1

Expr           ::= Number
					|| '(' Expr ')'      assoc => group
					|| Expr '**' Expr    assoc => right
					|| Expr '*' Expr     # Left associativity is by default.
					 | Expr '/' Expr
					|| Expr '+' Expr
					 | Expr '-' Expr

Number         ~ [\d]+

:discard       ~ whitespace

whitespace     ~ [\s]+
