invoke_for_each.cpp

/**
 * @brief Calls a callable for each passed parameter
 * @details If callable is a C++14 generic lambda (i.e. [](auto&& arg){};),
 * input parameters may be of different types
 */
template <typename Callable, typename... Args>
constexpr void InvokeForEach(const Callable& callable, Args&&... args)
{
	// The following approach relies on the fact that contents
	// of the array initializer list are evaluated from left to write
	// (which is guaranteed by the C++ standard), so the callable is
	// invoked for each argument in the same order in which the arguments
	// were passed into this function.
	// The more conventional way of doing things in variadic functions
	// would be making a solution via variadic recursion, but
	// there seems to be a consensus that it will produce a more bloated 
	// code because of recursive calls that may not be optimized away
	using ExpandAsArrayInitList = int[];
	ExpandAsArrayInitList{
		0, // NOTE: forces initializer list to be non-empty 
		(callable(std::forward<decltype(args)>(args)), // NOTE: comma operator at the end
			void(), // NOTE: protects from accidental usage of overloaded comma operator
			        // since comma operator can't be overloaded for void
			0       // NOTE: dummy value that is actually put into the array initializer
			        // list
		)... // NOTE: variadic parameter pack expansion
	};
}