tgmath.hheader. These are macros that expand to the appropriate function based on the type of the provided argument. For example, their are 6 different arc cosine functions: 3 for the different real floating point types and 3 for the different complex floating point types. If you
#include <tgmath.h>, a macro with the name
acosis exposed which will expand to a call to one of the 6 functions based on the argument type.
The type-generic mechanism employed to make this work was not exposed or made available to the programmer but was instead left up to implementation magic. C11 introduces the generic selection expression which provides a mechanism to make compile-time choices based on type allowing type-generic macros to be created using standard C constructs.
In this post I will introduce and explore some of the applications of the new generic selection.