%File: arithmetic.pro

%Line: a nondestructive arithmetic program

:- consult('gv.pro').

add(V1,V2,Result) :-
		  binding(V1,R1),
		  binding(V2,R2),
		  Value is R1 + R2,
		  assert(binding(Result,Value)).

sub(V1,V2,Result) :-
		  binding(V1,R1),
		  binding(V2,R2),
		  Value is R1 - R2,
		  assert(binding(Result,Value)).

mul(V1,V2,Result) :-
		  binding(V1,R1),
		  binding(V2,R2),
		  Value is R1 * R2,
		  assert(binding(Result,Value)).

div(V1,V2,Result) :-
		  binding(V1,R1),
		  binding(V2,R2),
		  Value is R1 / R2,
		  assert(binding(Result,Value)).

exp(V1,V2,Result) :-
		  binding(V1,R1),
		  binding(V2,R2),
		  Value is R1 ^ R2,
		  assert(binding(Result,Value)).