struct callable_traits

|callable_traits| captures elements of interest from function-like types (functions, function

pointers, and functors, including lambdas). Due to common usage patterns, const and non-const

functors are treated identically.

Member types:

|args| - a |parameter_pack| that captures the parameter types of the function. See

|parameter_pack| for usage and details.

|return_type| - the return type of the function.

|type| - the underlying functor or function pointer type. This member is absent if

|callable_traits| are requested for a raw function signature (as opposed to a

function pointer or functor; e.g. |callable_traits

<void

()>|).

|signature| - the type of the equivalent function.