listless.js

function emptyList() {
  return function(which) {
    return which(undefined, emptyList(), true);
  };
}

function prepend(head, tail) {
  return function(which) {
    return which(head, tail, false);
  };
}

function head(list) {
  return list(function(head, _tail, _isEmpty) {
    return head;
  });
}

function tail(list) {
  return list(function(_head, tail, _isEmpty) {
    return tail;
  });
}

function isEmpty(list) {
  return list(function(_head, _tail, isEmpty) {
    return isEmpty;
  });
}

function map(mapping, list) {
  if (isEmpty(list)) {
    return list;
  } else {
    return prepend(
      mapping(head(list)),
      map(mapping, tail(list))
    );
  }
}

function reduce(reduction, initialValue, list) {
  if (isEmpty(list)) {
    return initialValue;
  } else {
    return reduce(
      reduction,
      reduction(initialValue, head(list)),
      tail(list)
    );
  }
}

var example = prepend(
  1,
  prepend(2, prepend(3, emptyList()))
);

head(example); // => 1

head(
  map(function(i) {
    return i + 1;
  }, example)
); // => 2

reduce(
  function(sum, i) {
    return sum + i;
  },
  0,
  example
); // => 6