If we want to show primitive recursion for
sgn(x) = 0 if x = 0 and 1 otherwise
Is it enough to say that sgn(0) = 0 and sgn(x+1) = 1?
Is there any details omitting here or anything needed to be polished?
Also, to show that x monus y = (x-y) if x >= y and 0 otherwise, where we have the monus function N^2 --> N as primitive recusive, is it enough to say that:
x monus 1 is primitive recursive as 0 monus 1 = 0, but not sure what else to continue here.