Description

Test:: check the basic utilities for manipulating variadic template arguments.

single out and pick an argument designated by index
pick an argument with fallback on default construction
demonstrate usage by reordering the position of arguments

Definition at line 134 of file variadic-argument-picker-test.cpp.

Private Member Functions
void	check_pickArg ()

void	check_pickInit ()

void	check_reorderedArguments ()

virtual void	run (Arg)

void	verify_fixture ()

Static Private Member Functions
template<class... ARGS, size_t... idx>
static auto	call_with_reversed_arguments (IndexSeq< idx... >, ARGS &&...args)
	Demonstration of argument manipulation through metaprogramming. More...

Member Function Documentation

◆ call_with_reversed_arguments()

static auto call_with_reversed_arguments	(	IndexSeq< idx... >	,
		ARGS &&...	args
	)

inlinestaticprivate

Demonstration of argument manipulation through metaprogramming.

This function invokes the ubiquitous fun test function with arbitrary arguments, but it re-orders and even prunes arguments as dictated by the Index sequence parameter.

Remarks

Note some fine points:

the value of the parameter IndexSeq<idx...> is irrelevant
rather, its sole purpose is to pattern match against the type
we use IndexSeq just as an container to hold the sequence idx...
the expression within the function argument list expands the argument packs
and both of them are treated separately
the actual arguments are wrapped into a std::forward for perfect forwarding
but the key trick of the whole operation lies in the expansion of the idx... pack
note that idx without the ... sits within the template list of pickArg<idx>
while the corresponding expansion operator is outmost and thus works on the whole expression
and thus it is the idx... pack which actually drives the generation of several pickArg instantiations
in the end the net effect is that the Index sequence absolutely dictates which arguments are picked