implicit conversion shortens 64 bit to 32 bit

Question

Can someone explain why this causes the error stated in the title?

CGFloat dx = fabs(lastPoint.x - currentPoint.x);

Thanks

Answer 1

fabs() returns a double (64-bit), but CGFloat is defined to be a float (32-bit). It's generally harmless – I personally would even disable the compiler warning, as performing calculations using double values is typically at least as fast as using float values.

Answer 2

A better answer is to use #include <tgmath.h>. That header defines "adaptive" functions that call the correct function on whichever parameter size.

With that header included, you can simply call fabs without getting that warning (nor worrying about loss of precision caused by the use of the wrong function).