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CPP20Hackathon: Add more concepts and use them in pattern/forall #2012

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CPP20Hackathon: Add more concepts and use them in pattern/forall #2012

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65 changes: 65 additions & 0 deletions include/RAJA/pattern/forall-concepts.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,71 @@ template<typename T>
concept ForallParameterPack =
RAJA::expt::type_traits::is_ForallParamPack<camp::decay<T>>::value;



// Concept for strongly typed index types.
template < typename T >
concept StrongIndexType = !std::integral<T> && requires (T val)
{
{ stripIndexType(val) } -> std::integral;
};

// Concept index types or strongly typed index types.
// TODO: improve the name
template < typename T >
concept IndexTypeConcept = std::integral<T> || StrongIndexType<T>;

// Concept for types that may be callable.
// Use std::invokable when the full set of arguments is known.
template < typename B >
concept PotentialInvokable =
std::is_class_v<std::remove_cvref_t<B>> ||
std::is_union_v<std::remove_cvref_t<B>> ||

@artv3 artv3 Apr 23, 2026

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do we have callable unions in our applications?

std::is_function_v<std::remove_cvref_t<B>> ||
( std::is_pointer_v<std::remove_cvref_t<B>> &&
std::is_function_v<std::remove_cv_t<std::remove_pointer_t<std::remove_cvref_t<B>>>> );

consteval bool testPotentialInvokable() noexcept
{
using I = int;
using F = int();
struct S{};
union U{};
using L = decltype([]{});
static_assert(!PotentialInvokable<I>);
static_assert(!PotentialInvokable<I&>);

@johnbowen42 johnbowen42 Apr 20, 2026

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Could you make a variadic template that tries to substitute the pack into std::is_invocable?

static_assert(!PotentialInvokable<I*>);
static_assert(!PotentialInvokable<I[]>);
static_assert(PotentialInvokable<F>);
static_assert(PotentialInvokable<F&>);
static_assert(PotentialInvokable<F*>);
static_assert(PotentialInvokable<F*&>);
static_assert(!PotentialInvokable<F**>);
static_assert(!PotentialInvokable<F*[]>);
static_assert(PotentialInvokable<S>);
static_assert(PotentialInvokable<S&>);
static_assert(!PotentialInvokable<S*>);
static_assert(!PotentialInvokable<S[]>);
static_assert(PotentialInvokable<U>);
static_assert(PotentialInvokable<U&>);
static_assert(!PotentialInvokable<U*>);
static_assert(!PotentialInvokable<U[]>);
static_assert(PotentialInvokable<L>);
static_assert(PotentialInvokable<L&>);
static_assert(!PotentialInvokable<L*>);
static_assert(!PotentialInvokable<L[]>);
return true;
}
static_assert(testPotentialInvokable());

// Concept for forall param objects.
template < typename Arg >
concept ForallParam = std::is_base_of_v<expt::detail::ForallParamBase, std::remove_cvref_t<Arg>>;

// Concept for forall arguments that may be forall param objects or callables.
template < typename Arg >
concept ForallParamsAndBody = ForallParam<Arg> || PotentialInvokable<Arg>;

} // namespace RAJA

#endif
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