Matching semantics

At each input position, flexr selects the rule that consumes the most characters. If multiple rules consume the same number, the rule defined first wins.

rule(/==/) { emit :EQ }
rule(/=/) { emit :ASSIGN }

Input == produces EQ, regardless of the order above. Equal-length alternatives are resolved by definition order, so putting keyword rules before a broad identifier rule is the conventional way to reserve keywords.

The playground shows candidates and the winner for each scan step. The firstmatch backend is experimental because it changes this selection model.