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add tuple_size to camp::array #194

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add tuple_size to camp::array #194

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2751b87
add tuple_size to camp::array
gberg617 Mar 4, 2026
34d0659
moved array's tuple_size to the array header
gberg617 Jul 1, 2026
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7 changes: 7 additions & 0 deletions include/camp/array.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,9 @@

namespace camp
{
template <typename Tuple>
struct tuple_size;

///
/// Provides a portable std::array-like class.
///
Expand Down Expand Up @@ -284,6 +287,10 @@ CAMP_HOST_DEVICE constexpr void swap(array<T, N>& a, array<T, N>& b) noexcept(
a.swap(b);
}

template <typename T, size_t N>
struct tuple_size<array<T, N>> : ::camp::num<N> {
};

namespace detail
{
template <class T, std::size_t N, std::size_t... I>
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1 change: 1 addition & 0 deletions include/camp/tuple.hpp
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Expand Up @@ -19,6 +19,7 @@
#include <sstream>
#include <type_traits>

#include "camp/array.hpp"

@adayton1 adayton1 Jul 1, 2026

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This still seems backwards. tuple should be able to exist without knowing about array.

@adayton1 adayton1 Jul 1, 2026

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If array needs tuple_size from tuple.hpp, then just have array.hpp include tuple.hpp. But tuple should be able to stand alone independent of array.

@adayton1 adayton1 Jul 1, 2026

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Really the base declaration of tuple_size and tuple_element should be in a separate header that both tuple.hpp and array.hpp could include.

@MrBurmark MrBurmark Jul 2, 2026

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Where is camp apply defined? That's what this is all about, is that in some higher level common header?

@MrBurmark MrBurmark Jul 2, 2026

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Does it make more sense to change camp::apply to use std::tuple_size?

@gberg617 gberg617 Jul 2, 2026

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What about two separate headers: one for traits common to both array and tuple (such as tuple_size), and another for common implementations (such as apply, invoke, etc..)?

@MrBurmark MrBurmark Jul 2, 2026

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tuple_size isn't used in that many places, how about just using std::tuple_size as we should have been doing all along? We can make camp::tuple_size an alias for std::tuple_size.

@gberg617 gberg617 Jul 2, 2026

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Sure, I think something like that can work. My previous point was about moving camp's tuple_size and apply(...) to a separate header so that traits/methods that are common to both camp tuples and arrays don't live in tuple.hpp, but are instead included in there as well as array.hpp. Hopefully this would address the concerns that @adayton1 mentions above.

#include "camp/concepts.hpp"
#include "camp/map.hpp"

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