Match

[Not implemented yet - How important is this?]
The idea is that MATCH(N,x=>[F(x),G(x)],C) means if N = F(x) for some A then return G(x) else return C.
Same as(?) if Exists( n=>(N==F(X) , ) )
This function subtracts one from a natural number or returns zero if it is already zero:
If we have recursion as well we can implement more complicated functions using MATCH. $$\sqrt{1}$$