Arithmetic Operations

Basic arithmetic can be done on Lpp Numbers with the following.

plus x y

Function

minus x y

Function

times x y

Function

divide x y

Function

In these functions x and y must each be Lpp Numbers or int types and the returned result is a new Lpp Number. Their names describe what they do. It it worth mentioning however that divide does not truncate its value in any way, use the truncate function for that See Component Extractions on Numbers. If divide is given two number that do not divide evenly it will return an Lpp Ratio of the form x/y after it has been rationally canonicalized See Number Types. For example

     divide(L(12), L(4)) => 3            // evenly divides
     divide(L(13), L(4)) => 13/4         // doesn't so returns ratio
     divide(4, L(12)) => 1/3             // returns canonicalized ratio
     truncate(L(13), L(4)) => 3          // Use truncate function to truncate
     

inc x

Function

inc x delta

Function

dec x

Function

dec x delta

Function

These functions take an Lpp Number x and increments it in the case of inc and decrements it in the case of dec. The argument x is returned with the new value. Normally the increment or decrement is by 1, however if an optional second argument delta is given it must be an Lpp Number or int and the increment or decrement is by delta instead of 1.

Both inc and dec modify the object x so that most of the time a new object is not created. However there are cases where the a new object is created. This is when there is an object transition, for example from a SmallInteger to a BigInteger See Number Types. So in the following

     inc(x, 1024);             // OK but ...
     x = inc(x, 1024);         // this hadles object transition cases
     

if there is no transition expected then the first is fine. If a transition is possible then the second must be used and is the recommended form most of the time.

When there is an object transition Lpp automatically garbage collects the defunct object and returns the new incremented or decremented object. So in this case if the second code line above were not used then the new object would be lost and becomes a potential memory leak and x would point to deallocated memory.

negate x

Function

The negate function simply negates the Lpp number object that x points to. While this is similar to inc and dec in that it modified the object x, the object x is never transitioned to another type of object and hence does not have the transitioning concern. In the following

     negate(num);                    // Always OK
     num = negate(num);              // Does the same thing, but unnecessary
     other = negate(num);
     

the first is always safe to do and recommended, however the second works also but in unnecessary. The third would both negate num and set other to the negated num.

gcd x y

Function

The gcd function returns the greatest common divisor of x and y each of which must be an Lpp Integer or int type. The result is always a positive Lpp Integer. Here are some examples

     gcd(108, L(117)) => 9
     gcd(L(123), -48) => 3
     gcd(gcd(a, b), c);       // Returns the gcd of a b and c