Harvesting along a line

harvestline.sw

def ifC : cmd bool -> cmd a -> cmd a -> cmd a = \test. \then. \else.
  b <- test; if b then else
end

def x2 = \c. c;c end
def x4 = \c. x2 c; x2 c end
def x8 = \c. x4 c; x4 c end
def x16 = \c. x8 c; x8 c end
def x32 = \c. x16 c; x16 c end
def x64 = \c. x32 c; x32 c end
def x128 = \c. x64 c; x64 c end
def x256 = \c. x128 c; x128 c end
def x512 = \c. x256 c; x256 c end
def x1024 = \c. x512 c; x512 c end

// Harvest a specific item for a certain distance along a straight line, 
// then turn around and come back. Use it as in 'harvestline x32 "rock"'.
// This is useful in the early game
// since it only requires a lambda and a branch predictor, and doesn't 
// require you to know the exact distances to specific items, just that
// there are some items along a line.
def harvestline = \rep. \thing.
  rep {
    ifC (ishere thing) (grab; return ()) noop;
    move
  };
  turn back;
  rep move
end