lama_byterun/stdlib/Lazy.lama

-- Lazy.
-- (C) Dmitry Boulytchev, JetBrains Research, St. Petersburg State University, 2020
--
-- Deferred computations.

public fun makeLazy (f) {
  var value, set = false;
  
  fun () {
    if set
    then value
    else
      var c; -- need this temporary since in value := f () value would
               -- create an intermediate managed pointer
      set   := true;
      c     := f ();
      value := c;
      c
    fi
  } 
}

public fun force (f) {
  f ()
}