Solidity Value Types Function Types 3

library ArrayUtilities {
  // internal functions can be used in internal library functions because
  // they will be part of the same code context
  function map(uint[] memory self, function (uint) returns (uint) f)
    internal
    returns (uint[] memory r)
  {
    r = new uint[](self.length);
    for (uint i = 0; i < self.length; i++) {
      r[i] = f(self[i]);
    }
  }
  function reduction(
    uint[] memory self,
    function (uint, uint) returns (uint) f
  )
    internal
    returns (uint r)
  {
    r = self[0];
    for (uint i = 1; i < self.length; i++) {
      r = f(r, self[i]);
    }
  }
  function rangeTo(uint length) internal returns (uint[] memory r) {
    r = new uint[](length);
    for (uint i = 0; i < r.length; i++) {
      r[i] = i;
    }
  }
}

contract Pyramid {
  using ArrayUtilities for *;
  function pyramid(uint l) returns (uint) {
    return ArrayUtilities.range(l).map(square).reduce(sum);
  }
  function squareResult(uint a) internal returns (uint) {
    return a * a;
  }
  function sumResult(uint a, uint b) internal returns (uint) {
    return a + b;
  }
}