Ch2, Ex11

Kernel transform of IsEven:

proc {IsEven X ?R}
   local T in
      T = X==0
      if T then true else S=X-1 in {IsOdd S R} end
   end
end 

this is clearly tail recursive, similarly we can see IsOdd is also tail recursive, hence calls {IsOdd N} and {IsEven N} will execute with constant stack size.