result.hpp File Reference

Intermediary value object to represent »either« an operation result or a failure. More...

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Description

Intermediary value object to represent »either« an operation result or a failure.

Some operation might have produced a value result or failed with an exception. Typically, the Result token is used inline — immediately either invoking one of the member function or employing the built-in result type conversion. It will be copyable iff the result value is copyable. There is an implicit valid or failure state, which can be tested. Any attempt to get the value of an invalid result token will cause an exception to be thrown.

• Result<void>(bool) can be used as a success marker
• a Result instance can be created by perfect forwarding from any type
• any exception is supported for failure, wile direct construction is limited to lumiera::Error (to avoid ambiguities in ctor overload resolution)
• an arbitrary functor or callable can be invoked, capturing the result.

  Todo:

  an option-style interface could be provided for the »right value« (i.e. the exception caught), in case this turns out to be of any use; this kind of API design however is anything than trivial, given that any value can be thrown as exception in C++

  See also

  vault::ThreadJoinable usage example

  Result_test

Definition in file result.hpp.

#include "lib/error.hpp"
#include "lib/item-wrapper.hpp"
#include "lib/meta/util.hpp"
#include <type_traits>
#include <exception>
#include <utility>

Namespaces
namespace	lib
	Implementation namespace for support and library code.

Classes
class	Result< void >
	The base case is just to capture success or failure, without returning any value result. More...
class	Result< RES >
	Representation of the result of some operation, EITHER a value or a failure. More...

Functions
template<typename VAL , typename = lib::meta::disable_if<std::is_invocable<VAL>>>
	Result (VAL &&) -> Result< VAL >
	deduction guide: allow perfect forwarding of a any result into the ctor call.
template<typename FUN , typename... ARGS>
	Result (FUN &&, ARGS &&...) -> Result< std::invoke_result_t< FUN, ARGS... > >
	deduction guide: find out about result value to capture from a generic callable.