precompile_direct.sol

contract Precompile {
  function foo (bytes) returns (bytes32);
}

contract Testcontract {
  bytes32 last;

  event Debug(string message, bytes32 res);

  Precompile prec = Precompile(0x0000000000000000000000000000000000000002);

  function testMe () {
    bytes memory s = "hello";
    last = prec.foo("hello");
    Debug("testMe()", last);
    Debug("sha", sha256(s));
  }
  
  function test () returns (bytes32 b) {
      string memory x = "hello";
      bytes memory r;
      
      uint len = bytes(x).length;

      assembly {
          let a := 0x0000000000000000000000000000000000000002
          let v := 0
          
          call(200000, a, v, add(x,0x20), len, r, 0x20)
          pop
          b := mload(r)
      }
  }

}