gistfile1.txt

/*
 * Classic example grammar, which recognizes simple arithmetic expressions like
 * "2*(3+4)". The parser generated from this grammar then computes their value.
 */

start
  = additive

additive
  = left:multiplicative "+" right:additive { return {op: '+', toks: [left, right]}; }
  / multiplicative

multiplicative
  = left:primary "*" right:multiplicative { return {op: '*', toks: [left, right]}; }
  / primary

primary
  = integer
  / "(" additive:additive ")" { return additive }

integer
  = digits:[0-9]+ { return parseInt(digits.join("")) }