What is the point of using 'f' when assigning a value to a CGFloat?

Question

I see this all the time:

CGFloat someCGFloat = 1.2f;

Why is the \'f\' used? If the CGFloat is defined as float, the v

Answer 1

1.0 by default is double, if the right value is 1.2 there is an implicit cast, and the value gets casted from double to float (the cast isn't a runtime operation). In this case it's not important to call it 1.2f. Programmers mostly abuse it, but there are cases where it's really important.

For example:

float var= 1.0e-45;
NSLog(@"%d",var==1.0e-45);

This prints zero, because 1.0e-45 is too small to be stored into a single precision floating point variable, so it becomes equal to zero. Writing var==1.0e-45f changes the result.

Using format specifiers is important mostly when writing expressions, and since the left value is a float you expect that also the expression gets treated as a float, but that's not what happens.

A more striking case is when using the l format specifier on a number that gets shifted so much to become zero, and get surprised about the result:

long var= 1<<32;  // I assume that an int takes 4 bytes and a long 8 bytes

The result is zero, and writing 1l<<32 completely changes the result.