dfs.sw

// A convenient version of if that takes a cmd bool instead of a bool
def ifC : forall a. cmd bool -> cmd a -> cmd a -> cmd a =
  \test. \thn. \els. b <- test; if b thn els
end

// Do a DFS to harvest trees to the west and north.
// Position the robot on a tree near the southeast corner of a
// forest for best effect.  The robot will collect a bunch
// of trees and return to its original starting point.
// Capabilities required: recursion, lambdas, scanner
def dfs : cmd () = {
  ifC (ishere "tree") {
    grab;
    turn west;
    ifC blocked {} {move; dfs; turn east; move};
    turn north;
    ifC blocked {} {move; dfs; turn south; move};
  } {}
}
end