function generateEither(genA, genB) {
  var result = generatorBless(function (size) { // eslint-disable-line consistent-return
    var n = random(0, 1);
    switch (n) {
      case 0: return either.left(genA(size));
      case 1: return either.right(genB(size));
      // no default
    }
  });

  return utils.curried3(result, arguments);
}
- `generator.either(genA: generator a, genB: generator b): generator (either a b)`