C++ utilities and backports

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::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::IsNumber< T >
	Whether this type acts as a scalar in the context of (hierarchically blocked) containers. More...
struct	Dune::has_nan< T >
	Whether this type has a value of NaN. More...
struct	Dune::is_indexable< 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::is_range< 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...
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.
#define	DUNE_UNUSED_PARAMETER(parm)   static_cast<void>(parm)
	A macro to mark intentionally unused function parameters with.

Typedefs
template<bool value>
using	Dune::Std::bool_constant = std::integral_constant< bool, value >
	A template alias for std::integral_constant<bool, value> More...
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 (see N3911). The workhorse for C++11 SFINAE-techniques.
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.

Functions
template<typename T , std::size_t n>
std::array< T, n >	Dune::fill_array (const T &t)
	Create an array and fill it with copies of the provided value. More...
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<class F , class ArgTuple >
decltype(auto)	Dune::Std::apply (F &&f, ArgTuple &&args)
	Apply function with arguments given as tuple. 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<typename T , typename... Args>
Impl::MakeUniqueHelper< T >::NonArrayUniquePtr	Dune::Std::make_unique (Args &&... args)
	Implementation of std::make_unique to be introduced in C++14. More...
template<typename T >
Impl::MakeUniqueHelper< T >::UnknownBoundArrayUniquePtr	Dune::Std::make_unique (size_t n)
	Implementation of std::make_unique to be introduced in C++14. 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...

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.

#include <dune/common/deprecated.hh>

This is a preprocessor define which can be used to mark functions, typedefs, enums and other stuff deprecated. If something is marked deprecated, users are advised to migrate to the new interface, since it will probably be removed in the next release of Dune.

DUNE_DEPRECATED currently works with g++ and clang++. For other compilers it will be defined empty. This way the user will not get any deprecation warning, but at least his code still compiles (well, until the next Dune release, that is).

Here are some examples how to mark different stuff deprecated:

• Classes

  class DUNE_DEPRECATED Class {}; // 1)
  class Class {} DUNE_DEPRECATED; // 2)

  Both forms do not work properly with g++-4.1: no deprecation warning will be given, although the code still compiles. 1) should be preferred over 2) since 2) does not work with clang++-1.1 (again, no warning given but code still compiles, works with clang++-3.1)
• Template classes

  template<class T>
  class DUNE_DEPRECATED Class {}; // 1)
  template<class T>
  class Class {} DUNE_DEPRECATED; // 2)

  This works works with g++ >=4.3 only; g++-4.1 and clang++ compile the code without warning in both cases. Furthermore, the warning is only triggered when copying an object of that template class, neither making a typedef nor simply creating such an object emit the warning. It is thus recommended that some essential class member be marked deprecated as well, if possible.
• Member constants

  template<typename T> struct Class {
  static const int c0 DUNE_DEPRECATED = 0;
  static const int DUNE_DEPRECATED c1 = 1;
  };

  Works with g++-4.1, g++ >=4.3 and clang++3.1. No warning but clean compile with clang++-1.1.
• Member enumerators

  template<typename T> struct Class {
  enum enumeration { enumerator = 0 };
  };

  No form of deprecation is known that does not trigger an error on most compilers.
• Member functions

  template<typename T> struct Class {
  void frob() DUNE_DEPRECATED {}
  }; // 1)
  template<typename T> struct Class {
  void DUNE_DEPRECATED frob() {}
  }; // 2)
  template<typename T> struct Class {
  DUNE_DEPRECATED void frob() {}
  }; // 3)

  With g++ only 2) emits a warning for templated member functions.

DUNE_DEPRECATED_MSG

#define DUNE_DEPRECATED_MSG

(

text

)

DUNE_DEPRECATED

Mark some entity as deprecated.

#include <dune/common/deprecated.hh>

This is a preprocessor define which can be used to mark functions, typedefs, enums and other stuff deprecated and to also specify a hint what replaces the given functionality. If something is marked deprecated, users are advised to migrate to the new interface, since it will probably be removed in the next release of Dune.

DUNE_DEPRECATED_MSG currently works only for compilers which support the attribute attribute((deprecated("message")). For other compilers it will be defined empty. This way the user will not get any deprecation warning, but at least his code still compiles (well, until the next Dune release, that is).

Here are some examples how to mark different stuff deprecated:

• Classes

  class DUNE_DEPRECATED_MSG("In the future, please use 'Glass'") Class {}; // 1)
  class Class {} DUNE_DEPRECATED_MSG("In the future, please use 'Glass'"); // 2)

  For both forms, deprecation warnings and the additional hint "In the future, please use 'Glass'" will be printed on compilers which support it (e.g. G++ >= 4.5.0, clang++ >= 1.1). For compilers which support deprecating but do not take an additional hint (e.g. G++ < 4.5.0), only the deprecation warning is printed, and finally compilers which do not support deprecation of code won't print anything, but the code will still compile. 1) should be preferred over 2) since 2) does not work with clang++-1.1 (again, no warning will be given but code still compiles)
• Template classes

  template<class T>
  class DUNE_DEPRECATED_MSG("In the future, please use 'Glass'") Class {}; // 1)
  template<class T>
  class Class {} DUNE_DEPRECATED_MSG("In the future, please use 'Glass'"); // 2)

  This works works with g++ >= 4.5, clang++ until at least version 1.1 will compile the code without warning in both cases. Furthermore, the warning is only triggered when copying an object of that template class, neither making a typedef nor simply creating such an object emit the warning. It is thus recommended that some essential class member be marked deprecated as well, if possible.
• Member constants

  template<typename T> struct Class {
  static const int c0 DUNE_DEPRECATED_MSG("c2 is the new hype") = 0;
  static const int DUNE_DEPRECATED_MSG("c2 is the new hype") c1 = 1;
  };

  Works without printing the hint on g++-4.1, g++-4.3, g++-4.4 and fully on g++ >= 4.5. Works for clang++-3.1. No warning but clean compile with clang++-1.1.
• Member enumerators

  template<typename T> struct Class {
  enum enumeration { enumerator = 0 };
  };

  No form of deprecation is known that does not trigger an error on most compilers.
• Member functions

  template<typename T> struct Class {
  void frob() DUNE_DEPRECATED_MSG("use frog") {}
  }; // 1)
  template<typename T> struct Class {
  void DUNE_DEPRECATED_MSG("use frog") frob() {}
  }; // 2)
  template<typename T> struct Class {
  DUNE_DEPRECATED_MSG("use frog") void frob() {}
  }; // 3)

  With g++ only 2) emits a warning for templated member functions.

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.

DUNE_NO_DEPRECATED_BEGIN
some_deprecated_function();
another_deprecated_function();
DUNE_NO_DEPRECATED_END

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

Typedef Documentation

bool_constant

template<bool value>

using Dune::Std::bool_constant = typedef std::integral_constant<bool, value>

A template alias for std::integral_constant<bool, value>

Template Parameters

value

Boolean value to encode as std::integral_constant<bool, value>

detected_or

template<typename Default , template< typename... > class Op, typename... Args>

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 for std::true_type and type is an alias for Op<Args...>.
• If Op<Args...> is invalid, value_t is an alias for std::false_type and type is an alias for Default.

This can be used to safely extract a nested typedef from a type T that might not define the typedef:

struct A { using size_type = int ; };
struct B;
 
template<typename T>
using SizeType = typename T::size_type;
 
// this extracts the nested typedef for int
using st_a = typename detected_or<std::size_t,SizeType,A>::type;
// as there is no nested typedef in B, this yields std::size_t
using st_b = typename detected_or<std::size_t,SizeType,B>::type;

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

template<typename Default , template< typename... > class Op, typename... Args>

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

template<template< typename... > class Op, typename... Args>

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

template<template< typename... > class Op, typename... Args>

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

template<typename Target , template< typename... > class Op, typename... Args>

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

template<typename Expected , template< typename... > class Op, typename... Args>

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.

Function Documentation

apply()

template<class F , class ArgTuple >

decltype(auto) Dune::Std::apply	(	F &&	f,
		ArgTuple &&	args
	)

Apply function with arguments given as tuple.

Parameters

f	A callable object
args	Tuple of arguments

This will call the function with arguments generated by unpacking the tuple.

Referenced by Dune::LDL< BCRSMatrix< FieldMatrix< T, n, m >, A > >::apply(), Dune::SPQR< BCRSMatrix< FieldMatrix< T, n, m >, A > >::apply(), Dune::SuperLU< BCRSMatrix< FieldMatrix< T, n, m >, A > >::apply(), Dune::UMFPack< BCRSMatrix< FieldMatrix< T, n, m >, A > >::apply(), Dune::TopologyFactory< Traits >::create(), Dune::fillGridViewInfoSerial(), Dune::GenericLocalFiniteElement< BasisF, CoeffF, InterpolF >::GenericLocalFiniteElement(), and Dune::SizeCache< GridImp >::size().

fill_array()

template<typename T , std::size_t n>

std::array< T, n > Dune::fill_array

(

const T &

t

)

Create an array and fill it with copies of the provided value.

Note

This method is Dune-specific and not part of any C++ standard.

Deprecated:

Use Dune::filledArray() from <dune/common/filledarray.hh>.

Deprecated:

"Use Dune::filledArray() from <dune/common/filledarray.hh>"

handle_proxy_member_access()

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).

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:

class iterator
{
  ...
 
  decltype(handle_proxy_member_access(implementation.dereference()))
  operator->() const
  {
    return handle_proxy_member_access(implementation.dereference());
  }
 
  ...
};

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()

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  )

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()

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.

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.

make_unique() [1/2]

template<typename T , typename... Args>

Impl::MakeUniqueHelper< T >::NonArrayUniquePtr Dune::Std::make_unique ( Args &&...  args )

delete

Implementation of std::make_unique to be introduced in C++14.

Template Parameters

T	Nonarray type of object to be constructed
...Args	Parameter types for constructor of T

Parameters

args	Arguments to be passed to constructor of T

This fallback implementation using perfect forwarding as proposed by Herb Sutter in http://herbsutter.com/gotw/_102/

make_unique() [2/2]

template<typename T >

Impl::MakeUniqueHelper< T >::UnknownBoundArrayUniquePtr Dune::Std::make_unique

(

size_t

n

)

Implementation of std::make_unique to be introduced in C++14.

Template Parameters

T	Array type of unknown bound

Parameters

n	Size of array to allocate

orderedOverload()

template<class... F>

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()

template<class... F>

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.

Variable Documentation

is_detected_convertible_v

template<typename Target , template< typename... > class Op, typename... Args>

constexpr bool Dune::Std::is_detected_convertible_v = is_detected_convertible<Target,Op,Args...>::value

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

template<typename Expected , template< typename... > class Op, typename... Args>

constexpr bool Dune::Std::is_detected_exact_v = is_detected_exact<Expected,Op,Args...>::value

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

template<template< typename... > class Op, typename... Args>

constexpr bool Dune::Std::is_detected_v = is_detected<Op,Args...>::value

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.