Dune Core Modules (2.8.0)
Standard library features backported from newer C++ versions or technical specifications and DUNE-specific utilities. More...
Files | |
file | keywords.hh |
Definitions of several macros that conditionally make C++ syntax available. | |
file | proxymemberaccess.hh |
infrastructure for supporting operator->() on both references and proxies | |
Namespaces | |
namespace | Dune::Std |
Namespace for features backported from new C++ standards. | |
Classes | |
class | Dune::IteratorRange< Iterator > |
Simple range between a begin and an end iterator. More... | |
struct | Dune::Std::is_callable< D, R > |
Traits class to check if function is callable. More... | |
struct | Dune::Std::is_callable< F(Args...), R > |
Traits class to check if function is callable. More... | |
struct | Dune::Std::is_invocable< F, Args > |
Traits class to check if function is invocable. More... | |
struct | Dune::Std::is_invocable_r< R, F, Args > |
Traits class to check if function is invocable and the return type is compatible. More... | |
struct | Dune::Std::nonesuch |
Type representing a lookup failure by std::detected_or and friends. More... | |
struct | Dune::Std::conjunction< B > |
forms the logical conjunction of the type traits B... More... | |
struct | Dune::Std::disjunction< B > |
forms the logical disjunction of the type traits B... More... | |
struct | Dune::Std::negation< B > |
forms the logical negation of the type traits B... More... | |
struct | Dune::Empty |
Just an empty class. More... | |
struct | Dune::IsInteroperable< T1, T2 > |
Checks whether two types are interoperable. More... | |
struct | Dune::EnableIfInterOperable< T1, T2, Type > |
Enable typedef if two types are interoperable. More... | |
struct | Dune::AlwaysFalse< T > |
template which always yields a false value More... | |
struct | Dune::AlwaysTrue< T > |
template which always yields a true value More... | |
struct | Dune::IsCallable< D, R > |
Check if a type is callable with ()-operator and given arguments. More... | |
struct | Dune::IsCallable< F(Args...), R > |
Check if a type is callable with ()-operator and given arguments. More... | |
struct | Dune::IsNumber< T > |
Whether this type acts as a scalar in the context of (hierarchically blocked) containers. More... | |
struct | Dune::HasNaN< T > |
Whether this type has a value of NaN. More... | |
struct | Dune::IsIndexable< T, I > |
Type trait to determine whether an instance of T has an operator[](I), i.e. whether it can be indexed with an index of type I. More... | |
struct | Dune::IsIterable< T, typename > |
typetrait to check that a class has begin() and end() members More... | |
struct | Dune::IsTuple< T > |
Check if T is a std::tuple<...> More... | |
struct | Dune::IsTupleOrDerived< T > |
Check if T derived from a std::tuple<...> More... | |
struct | Dune::IsIntegralConstant< T > |
Check if T is an std::integral_constant<I, i> More... | |
struct | Dune::SizeOf< T > |
Compute size of variadic type list. More... | |
struct | Dune::IntegerSequenceEntry< IntegerSequence, index > |
Get entry of std::integer_sequence. More... | |
struct | Dune::AutonomousValueType< T > |
Type free of internal references that T can be converted to. More... | |
struct | Dune::AutonomousValueType< T & > |
Specialization to remove lvalue references. More... | |
struct | Dune::AutonomousValueType< T && > |
Specialization to remove rvalue references. More... | |
struct | Dune::AutonomousValueType< const T > |
Specialization to remove const qualifiers. More... | |
struct | Dune::AutonomousValueType< volatile T > |
Specialization to remove volatile qualifiers. More... | |
struct | Dune::AutonomousValueType< std::vector< bool >::reference > |
Specialization for the proxies of vector<bool> More... | |
struct | Dune::AutonomousValueType< volatile const T > |
Specialization to remove both const and volatile qualifiers. More... | |
class | Dune::Std::to_false_type< T > |
template mapping a type to std::false_type More... | |
class | Dune::Std::to_true_type< T > |
template mapping a type to std::true_type More... | |
Macros | |
#define | DUNE_ASSERT_AND_RETURN(C, X) (!(C) ? throw [&](){assert(!#C);return 0;}() : 0), X |
Asserts a condition and return on success in constexpr context. More... | |
#define | DUNE_DEPRECATED |
Mark some entity as deprecated. More... | |
#define | DUNE_DEPRECATED_MSG(text) DUNE_DEPRECATED |
Mark some entity as deprecated. More... | |
#define | DUNE_NO_DEPRECATED_BEGIN ... |
Ignore deprecation warnings (start) More... | |
#define | DUNE_NO_DEPRECATED_END ... |
Ignore deprecation warnings (end) More... | |
#define | DUNE_UNUSED |
A macro for marking variables that the compiler mistakenly flags as unused, which sometimes happens due to templates. More... | |
#define | DUNE_UNUSED_PARAMETER(parm) static_cast<void>(parm) |
Typedefs | |
template<typename Default , template< typename... > class Op, typename... Args> | |
using | Dune::Std::detected_or = Impl::detector< Default, void, Op, Args... > |
Detects whether Op<Args...> is valid and makes the result available. More... | |
template<template< typename... > class Op, typename... Args> | |
using | Dune::Std::is_detected = typename detected_or< nonesuch, Op, Args... >::value_t |
Detects whether Op<Args...> is valid. More... | |
template<template< typename... > class Op, typename... Args> | |
using | Dune::Std::detected_t = typename detected_or< nonesuch, Op, Args... >::type |
Returns Op<Args...> if that is valid; otherwise returns nonesuch. More... | |
template<typename Default , template< typename... > class Op, typename... Args> | |
using | Dune::Std::detected_or_t = typename detected_or< Default, Op, Args... >::type |
Returns Op<Args...> if that is valid; otherwise returns the fallback type Default . More... | |
template<typename Expected , template< typename... > class Op, typename... Args> | |
using | Dune::Std::is_detected_exact = std::is_same< Expected, detected_t< Op, Args... > > |
Checks whether Op<Args...> is Expected without causing an error if Op<Args...> is invalid. More... | |
template<typename Target , template< typename... > class Op, typename... Args> | |
using | Dune::Std::is_detected_convertible = std::is_convertible< Target, detected_t< Op, Args... > > |
Checks whether Op<Args...> is convertible to Target without causing an error if Op<Args...> is invalid. More... | |
template<class... Types> | |
using | Dune::void_t = typename Impl::voider< Types... >::type |
Is void for all valid input types. The workhorse for C++11 SFINAE-techniques. More... | |
template<class Type > | |
using | Dune::field_t = typename FieldTraits< Type >::field_type |
Convenient access to FieldTraits<Type>::field_type. | |
template<class Type > | |
using | Dune::real_t = typename FieldTraits< Type >::real_type |
Convenient access to FieldTraits<Type>::real_type. | |
template<class T > | |
using | Dune::AutonomousValue = typename AutonomousValueType< T >::type |
Type free of internal references that T can be converted to. More... | |
Functions | |
template<class... F> | |
auto | Dune::overload (F &&... f) |
Create an overload set. More... | |
template<class... F> | |
auto | Dune::orderedOverload (F &&... f) |
Create an ordered overload set. More... | |
template<typename T > | |
pointer_or_proxy_holder | Dune::handle_proxy_member_access (T &&t) |
Transparent support for providing member access to both lvalues and rvalues (temporary proxies). More... | |
template<typename... Args> | |
std::array< typename std::common_type< Args... >::type, sizeof...(Args)> | Dune::Std::make_array (const Args &... args) |
Create and initialize an array. More... | |
template<class T , T... t, std::size_t index> | |
constexpr auto | Dune::integerSequenceEntry (std::integer_sequence< T, t... >, std::integral_constant< std::size_t, index > i) |
Get entry of std::integer_sequence. More... | |
template<class T > | |
constexpr AutonomousValue< T > | Dune::autoCopy (T &&v) |
Autonomous copy of an expression's value for use in auto type deduction. More... | |
Variables | |
template<template< typename... > class Op, typename... Args> | |
constexpr bool | Dune::Std::is_detected_v = is_detected<Op,Args...>::value |
Detects whether Op<Args...> is valid and makes the result available as a value. More... | |
template<typename Expected , template< typename... > class Op, typename... Args> | |
constexpr bool | Dune::Std::is_detected_exact_v = is_detected_exact<Expected,Op,Args...>::value |
Convenient access to the result value of is_detected_exact. More... | |
template<typename Target , template< typename... > class Op, typename... Args> | |
constexpr bool | Dune::Std::is_detected_convertible_v = is_detected_convertible<Target,Op,Args...>::value |
Convenient access to the result value of is_detected_convertible. More... | |
Detailed Description
Standard library features backported from newer C++ versions or technical specifications and DUNE-specific utilities.
Macro Definition Documentation
◆ DUNE_ASSERT_AND_RETURN
#define DUNE_ASSERT_AND_RETURN | ( | C, | |
X | |||
) | (!(C) ? throw [&](){assert(!#C);return 0;}() : 0), X |
Asserts a condition and return on success in constexpr context.
The macro DUNE_ASSERT_AND_RETURN can be used as expression in the return statement of a constexpr function to have assert() and constexpr at the same time. It first uses assert for the condition given by the first argument and then returns the value of the second argument.
◆ DUNE_DEPRECATED
#define DUNE_DEPRECATED |
Mark some entity as deprecated.
- Deprecated:
- Use C++14's
instead. It will be removed after Dune 2.8. Be aware that it must be sometimes placed at different position in the code.
◆ DUNE_DEPRECATED_MSG
#define DUNE_DEPRECATED_MSG | ( | text | ) | DUNE_DEPRECATED |
Mark some entity as deprecated.
- Deprecated:
- Use C++14's
instead. It will be removed after Dune 2.8. Be aware that it must be sometimes placed at different position in the code.
◆ DUNE_NO_DEPRECATED_BEGIN
#define DUNE_NO_DEPRECATED_BEGIN ... |
Ignore deprecation warnings (start)
This macro can be used together with DUNE_NO_DEPRECATED_END
to mark a block in which deprecation warnings are ignored. This can be useful for implementations of deprecated methods that call other deprecated methods or for testing deprecated methods in the testsuite.
- Warning
- This macro must always be used together with
DUNE_NO_DEPRECATED_END
◆ DUNE_NO_DEPRECATED_END
#define DUNE_NO_DEPRECATED_END ... |
Ignore deprecation warnings (end)
- Warning
- This macro must always be used together with
DUNE_NO_DEPRECATED_BEGIN
◆ DUNE_UNUSED
#define DUNE_UNUSED |
A macro for marking variables that the compiler mistakenly flags as unused, which sometimes happens due to templates.
- Deprecated:
- Use C++17's
instead. This macro will be removed after Dune 2.8. Be aware that it must be sometimes placed at a different position in the code.
◆ DUNE_UNUSED_PARAMETER
#define DUNE_UNUSED_PARAMETER | ( | parm | ) | static_cast<void>(parm) |
A macro to mark intentionally unused function parameters with.
If possible use C++17's
instead. Due to a bug prior to GCC 9.3 it cannot be used for the first argument of a constructor (bug 81429).
Typedef Documentation
◆ AutonomousValue
using Dune::AutonomousValue = typedef typename AutonomousValueType<T>::type |
Type free of internal references that T
can be converted to.
Specialize AutonomousValueType
to add your own mapping. Use autoCopy()
to convert an expression of type T
to AutonomousValue<T>
.
This type alias determines a type that T
can be converted to, but that will be free of references to other objects that it does not manage. In practice it will act like std::decay_t
, but in addition to removing references it will also determine the types that proxies stand in for, and the types that expression templates will evaluate to.
"Free of references" means that the converted object will always be valid and does not alias any other objects directly or indirectly. The "other
objects that it does not manage" restriction means that the converted object may still contain internal references, but they must be to resources that it manages itself. So, an std::vector
would be an autonomous value even though it contains internal references to the storage for the elements since it manages that storage itself.
- Note
- For pointers, iterators, and the like the "value" for the purpose of
AutonomousValue
is considered to be the identity of the pointed-to object, so that object should not be cloned. But then you should hopefully never need an autonomous value for those anyway...
◆ detected_or
using Dune::Std::detected_or = typedef Impl::detector<Default,void,Op,Args...> |
Detects whether Op<Args...>
is valid and makes the result available.
This alias template is an alias for an unspecified class type with two nested typedefs
value_t
and type
. It can be used to detect whether the meta function call Op<Args...>
is valid and access the result of the call by inspecting the returned type, which is defined as follows:
- If
Op<Args...>
can be instantiated,value_t
is an alias forstd::true_type
andtype
is an alias forOp<Args...>
. - If
Op<Args...>
is invalid,value_t
is an alias forstd::false_type
andtype
is an alias forDefault
.
This can be used to safely extract a nested typedef
from a type T
that might not define the typedef
:
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.
◆ detected_or_t
using Dune::Std::detected_or_t = typedef typename detected_or<Default,Op,Args...>::type |
Returns Op<Args...>
if that is valid; otherwise returns the fallback type Default
.
This alias template can be used to instantiate Op<Args...>
in a context that is not SFINAE-safe by appropriately wrapping the instantiation and automatically falling back to Default
if instantiation fails.
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.
◆ detected_t
using Dune::Std::detected_t = typedef typename detected_or<nonesuch,Op,Args...>::type |
Returns Op<Args...>
if that is valid; otherwise returns nonesuch.
This alias template can be used to instantiate Op<Args...>
in a context that is not SFINAE-safe by appropriately wrapping the instantiation. If instantiation fails, the marker type nonesuch is returned instead.
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.
◆ is_detected
using Dune::Std::is_detected = typedef typename detected_or<nonesuch,Op,Args...>::value_t |
Detects whether Op<Args...>
is valid.
This alias template checks whether Op<Args...>
can be instantiated. It is equivalent to typename detected_or<nonesuch,Op,Args...>::value_t
.
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.
◆ is_detected_convertible
using Dune::Std::is_detected_convertible = typedef std::is_convertible<Target,detected_t<Op,Args...> > |
Checks whether Op<Args...>
is convertible to Target
without causing an error if Op<Args...>
is invalid.
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.
◆ is_detected_exact
using Dune::Std::is_detected_exact = typedef std::is_same<Expected,detected_t<Op,Args...> > |
Checks whether Op<Args...>
is Expected
without causing an error if Op<Args...>
is invalid.
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.
◆ void_t
using Dune::void_t = typedef typename Impl::voider<Types...>::type |
Is void for all valid input types. The workhorse for C++11 SFINAE-techniques.
Note, since c++17 there is also std::void_t
that should be preferred. But, due to an issue in the c++ standard, see CWG issue #1980. "Equivalent but not functionally-equivalent redeclarations", and a corresponding failure in some clang compilers, this tool is left here as a workaround. Use it if you want to specialize multiple classes using void_t
.
Function Documentation
◆ autoCopy()
|
constexpr |
Autonomous copy of an expression's value for use in auto
type deduction.
This function is an unproxyfier or an expression evaluator or a fancy cast to ensure an expression can be used in auto
type deduction. It ensures two things:
- The return value is a prvalue,
- the returned value is self-sufficient, or "autonomous".
The latter means that there will be no references into other objects (like containers) which are not guaranteed to be kept alive during the lifetime of the returned value.
An example usage would be
Since vector<bool>
may use proxies, auto value = bitvector[23];
would mean that the type of value
is such a proxy. The proxy keeps internal references into the vector, and thus can be invalidated by anything that modifies the vector – such as a later call to resize()
. autoCopy()
lets you work around that problem by copying the value referenced by the proxy and converting it to a bool
.
Another example would be an automatic differentiation library that lets you track the operations in a computation, and later ask for derivatives. Imagine that your operation involves a parameter function, and you want to use that function both with plain types and with automatic differentiation types. You might write the parameter function as follows:
If the automatic differentiation library is Adept, this would lead to use-after-end-of-life-bugs. The reason is that for efficiency reasons Adept does not immidiately evaluate the expression, but instead it constructs an expression object that records the kind of expression and references to the operands. The expression object is only evaluated when it is assigned to an object of some number type – which will only happen after the operands (v
and the temporary object representing 2
) have gone out of scope and been destroyed. Basically, Adept was invented before auto
and rvalue-references were a thing.
This can be handled with autoCopy()
:
Of course, autoCopy()
needs to be taught about the expression objects of Adept for this to work.
autoCopy()
will by default simply return the argument as a prvalue of the same type with cv-qualifiers removed. This involves one or more copy/move operation, so it will only work with types that are in fact copyable. And it will incur one copy if the compiler cannot use a move, such as when the type of the expression is a std::array
or a FieldMatrix
. (Any second copy that may semantically be necessary will be elided.)
To teach autoCopy()
about a particular proxy type, specialize Dune::AutonomousValueType
.
- Note
- Do not overload
Dune::autoCopy()
directly. It is meant to be found by unqualified or qualified lookup, not by ADL. There is little guarantee that your overload will be declared before the definition of internal Dune functions that useautoCopy()
. They would need the lazy binding provided by ADL to find your overload, but they will probably use unqualified lookup.
◆ handle_proxy_member_access()
pointer_or_proxy_holder Dune::handle_proxy_member_access | ( | T && | t | ) |
Transparent support for providing member access to both lvalues and rvalues (temporary proxies).
If an iterator facade (like entity iterators) wants to allow the embedded implementation to return either an (internally stored) reference or a temporary object and expose these two behaviors to enable performance optimizations, operator->() needs special handling: If the implementation returns a reference, operator->() in the facade can simply return the address of the referenced object, but if the returned object is a temporary, we need to capture and store it in a helper object to make sure it outlives the member access. This function transparently supports both variants. It should be used like this:
- Note
- This function exploits the special type deduction rules for unqualified rvalue references to distinguish between lvalues and rvalues and thus needs to be passed the object returned by the implementation.
◆ integerSequenceEntry()
|
constexpr |
Get entry of std::integer_sequence.
- Parameters
-
seq An object of type std::integer_sequence<...> i Index
- Returns
- The i-th entry of the integer_sequence encoded as std::integral_constant<std::size_t, entry>.
◆ make_array()
std::array< typename std::common_type< Args... >::type, sizeof...(Args)> Dune::Std::make_array | ( | const Args &... | args | ) |
Create and initialize an array.
- Note
- This method is a somewhat limited dune-specific version of make_array() as proposed for C++17 (see N4391, accepted May 2015). The differences are that this version should never be used with expliclitly given template arguments, or with std::reference_wrapper<...> arguments, and we do not give a diagnostic when anyone happens to do that.
- Deprecated:
- Use deduction guide of
std::array
orstd::to_array
.
◆ orderedOverload()
auto Dune::orderedOverload | ( | F &&... | f | ) |
Create an ordered overload set.
- Template Parameters
-
F List of function object types
- Parameters
-
f List of function objects
This returns an object that contains all operator() implementations of the passed functions. All those are available when calling operator() of the returned object.
In contrast to overload() these overloads are ordered in the sense that the first matching overload for the given arguments is selected and later ones are ignored. Hence such a call is never ambiguous.
Notice that the passed function objects are stored by value and must be copy-constructible.
◆ overload()
auto Dune::overload | ( | F &&... | f | ) |
Create an overload set.
- Template Parameters
-
F List of function object types
- Parameters
-
f List of function objects
This returns an object that contains all operator() implementations of the passed functions. All those are available when calling operator() of the returned object.
The returned object derives from those implementations such that it contains all operator() implementations in its overload set. When calling operator() this will select the best overload. If multiple overload are equally good this will lead to ambiguity.
Notice that the passed function objects are stored by value and must be copy-constructible.
Referenced by Dune::Functions::negatePredicate().
Variable Documentation
◆ is_detected_convertible_v
|
constexpr |
Convenient access to the result value of is_detected_convertible.
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.
◆ is_detected_exact_v
|
constexpr |
Convenient access to the result value of is_detected_exact.
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.
◆ is_detected_v
|
constexpr |
Detects whether Op<Args...>
is valid and makes the result available as a value.
This constexpr variable checks whether Op<Args...>
can be instantiated. It is equivalent to is_detected<Op,Args...>::value
.
- Note
- This functionality is part of the C++ library fundamentals TS v2 and might or might not became part of C++2a.