15.3.5 Auxilary Arithmetic Functions

We need to auxilariy functions to compute weighted sums and products for a given range of integers.

These functions can be easily defined by recursive procedures (or alternatively by looping relative to a global cells containing an integer):

<int.oz>=

%% defines weighted sums and products
functor 
import 
export 
   Sum
   Prod
define 
   fun{Sum N M F}   
      if M==N-1 then 0 else {F N}+{Sum N+1 M F} end  
   end  
   fun{Prod N M F}
      if M==N-1 then 1 else {F N}*{Prod N+1 M F} end  
   end 
end