Simple PEG.js dice roller

peg_dice.js

start
  = additive

additive
  = left:dice "+" right:additive { return left + right; }
  / left:dice "-" right:additive { return left - right; }
  / dice

dice
  = left:primary "d" right:primary { var s = 0; for(var i = 0; i < left; i++ ) { s += Math.floor(Math.random() * right) + 1; } return s; }
  / primary

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

integer "integer"
  = digits:[0-9]+ { return parseInt(digits.join(""), 10); }