Question

im totally new at stack overflow, I usually just research stuff myself but I just started using xcode 4.2 and I cant help finding it weird.

These are the issues:

why cant i multiply by (1/2) but i can by 0.5? If i try the first option it will think its 0.

and second, is this if statement wrong?

if (-1 < x < 0)

I could swear i have done that in other programming languages but it wont work here, so i had to change to if ((-1 < x) && (x < 0))

Thank you for your time.

Answer 1

This is nothing to do with Xcode, it’s to do with the C language.

The first issue:

x * (1 / 2)

The C compiler treats 1 and 2 as ints, and in integer math, 1 / 2 = 0. If you want to multiply as floats, you can do:

x * (1.0 / 2.0)

or

x * ((float) 1 / (float) 2)

In your second issue, the compiler will interpret (-1 < x < 0) as ((-1 < x) < 0), which is obviously not what you want, since (-1 < x) will return either 0 for false, or 1 for true. To do compound logic statements in C, you need to use && for AND or || for OR:

((-1 < x) && (x < 0))