The result is of type real when any of the arguments is a real. Otherwise, when any of the arguments is a rational the result is a rational. Only when both arguments are integers, the result is an integer.
In coroutining mode, if Number1 or Number2 are free variables, the call to +/3 is delayed until these variables are instantiated.
Success: +(5, 2, 7). +(5, -2.0, 3.0). Fail: +(1, 2, 7). Error: +(A, 2, 6). (Error 4). +(1, 2, 3.0). (Error 5). +(7 - 4, 2, 3). (Error 24). +(5, 2, r). (Error 24).