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Deduction guides #65

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68 changes: 59 additions & 9 deletions include/function2/function2.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1779,20 +1779,70 @@ using function_base = detail::function<
detail::config<IsOwning, IsCopyable, Capacity>,
detail::property<IsThrowing, HasStrongExceptGuarantee, Signatures...>>;

/// An owning copyable function wrapper for arbitrary callable types.
/// An owning copyable function wrapper.
template <typename... Signatures>
using function = function_base<true, true, capacity_default, //
true, false, Signatures...>;
struct function : public function_base<true, true, capacity_default, true, false, Signatures...> {
using base = function_base<true, true, capacity_default, true, false, Signatures...>;
using base::base;
};

/// An owning non copyable function wrapper for arbitrary callable types.
/// An owning non-copyable function wrapper.
template <typename... Signatures>
using unique_function = function_base<true, false, capacity_default, //
true, false, Signatures...>;
struct unique_function : public function_base<true, false, capacity_default, true, false, Signatures...> {
using base = function_base<true, false, capacity_default, true, false, Signatures...>;
using base::base;
};

/// A non owning copyable function wrapper for arbitrary callable types.
/// A non-owning copyable function wrapper.
template <typename... Signatures>
using function_view = function_base<false, true, capacity_default, //
true, false, Signatures...>;
struct function_view : public function_base<false, true, capacity_default, true, false, Signatures...> {
using base = function_base<false, true, capacity_default, true, false, Signatures...>;
using base::base;
};

// Helper to decompose member function pointer types
template <typename T>
struct function_traits;

template <typename R, typename C, typename... Args>
struct function_traits<R (C::*)(Args...)> {
using signature = R(Args...);
};

template <typename R, typename C, typename... Args>
struct function_traits<R (C::*)(Args...) const> {
using signature = R(Args...);
};

// Deduce the signature for a callable F
template <typename F, typename = void>
struct deduce_signature {};

// Handle function pointers
template <typename R, typename... Args>
struct deduce_signature<R(*)(Args...), void> {
using type = R(Args...);
};

// Handle functors (lambdas, objects with operator())
template <typename F>
struct deduce_signature<F, std::void_t<decltype(&F::operator())>> {
private:
using call_operator_t = decltype(&F::operator());
using traits = function_traits<call_operator_t>;
public:
using type = typename traits::signature;
};

// Deduction guides for each wrapper
template <typename F>
function(F) -> function<typename deduce_signature<F>::type>;

template <typename F>
unique_function(F) -> unique_function<typename deduce_signature<F>::type>;

template <typename F>
function_view(F) -> function_view<typename deduce_signature<F>::type>;

#if !defined(FU2_HAS_DISABLED_EXCEPTIONS)
/// Exception type that is thrown when invoking empty function objects
Expand Down