YES(?,O(n^2)) Problem: app(app(plus(),0()),y) -> y app(app(plus(),app(s(),x)),y) -> app(s(),app(app(plus(),x),y)) app(app(app(curry(),f),x),y) -> app(app(f,x),y) add() -> app(curry(),plus()) Proof: Matrix Interpretation Processor: dimension: 2 interpretation: [15] [add] = [8 ], [12] [curry] = [0 ], [0] [s] = [0], [1 2] [0] [app](x0, x1) = [0 1]x0 + x1 + [1], [2] [0] = [1], [2] [plus] = [5] orientation: [28] app(app(plus(),0()),y) = y + [8 ] >= y = y [1 2] [26] [1 2] [24] app(app(plus(),app(s(),x)),y) = [0 1]x + y + [8 ] >= [0 1]x + y + [8 ] = app(s(),app(app(plus(),x),y)) [1 4] [1 2] [18] [1 4] [1 2] [2] app(app(app(curry(),f),x),y) = [0 1]f + [0 1]x + y + [3 ] >= [0 1]f + [0 1]x + y + [2] = app(app(f,x),y) [15] [14] add() = [8 ] >= [6 ] = app(curry(),plus()) problem: Qed