Question

If I define these variables:

double x0, xn, h;
int n;

and I have this mathematical expression:

h = (xn - x0)/n;

Is it necessary that I cast n into double prior doing the division for maximum accuracy like in

h = (xn - x0)/ (double) n;

I wrote a program to check the above but both expressions give the same answers. I understand that C will promote the integer to double type as variables xn and x0 are of type double but strangely enough in a book, the second expression with casting was emphasized.

My question would be if I’m thinking right.

Thanks a lot…

Answer 1

Your understanding is correct, and the book you read is either mistaken or being over-cautious (like people who claim that you should always test 0 == x instead of x == 0). The expression without the cast should always give precisely the same result as the expression with the cast.