cpp0x.dd

Ddoc

$(COMMUNITY D and C++0x,


	$(P
	C++ is undergoing an upgrade to a new standard, commonly referred
	to as C++0x.
	This article covers the highlights of
	$(LINK2 $(NDOCS)2008/n2597.html, C++0x core language changes)
	and compares them with what is available in D.
	Since C++0x is far from being finalized,
	this article is subject to being obsoleted by new proposals and
	revisions to existing ones.
	C++0x standard library changes are not addressed here.
	TBD means To Be Determined.
	)

$(SECTION3 Proposed C++0x Features,

	$(UL
	$(LI $(RELATIVE_LINK2 rvalue-reference, A Proposal to Add an Rvalue Reference to the C++ Language))
	$(LI $(RELATIVE_LINK2 class-rvalue, Clarification of Initialization of Class Objects by rvalues))
	$(LI $(RELATIVE_LINK2 move-semantics, Extending Move Semantics To *this (Revision 2)))
	$(LI $(RELATIVE_LINK2 static-assert, static_assert))
	$(LI $(RELATIVE_LINK2 template-aliases, Template aliases for C++))
	$(LI $(RELATIVE_LINK2 extern-template, Extern template))
	$(LI $(RELATIVE_LINK2 variadic-templates, Variadic Templates))
	$(LI $(RELATIVE_LINK2 variadic-template-templates, Extending Variadic Template Template Parameters))
	$(LI $(RELATIVE_LINK2 nullptr, A name for the null pointer: nullptr))
	$(LI $(RELATIVE_LINK2 strong-enums, Strongly Typed Enums))
	$(LI $(RELATIVE_LINK2 extended-friends, Extended friend Declarations))
	$(LI $(RELATIVE_LINK2 constant-expressions, Generalized Constant Expressions))
	$(LI $(RELATIVE_LINK2 namespace-association, Namespace Association ("Strong Using")))
	$(LI $(RELATIVE_LINK2 c99-preprocessor, Synchronizing the C++ preprocessor with C99))
	$(LI $(RELATIVE_LINK2 alignment, Adding Alignment Support to the C++ Programming Language))
	$(LI $(RELATIVE_LINK2 conditional, Conditionally-Supported Behavior))
	$(LI $(RELATIVE_LINK2 undefined-behavior, Changing Undefined Behavior into Diagnosable Errors))
	$(LI $(RELATIVE_LINK2 long-long, Adding the long long type to C++))
	$(LI $(RELATIVE_LINK2 extended-integer-types, Adding extended integer types to C++))
	$(LI $(RELATIVE_LINK2 delegating-ctors, Delegating Constructors))
	$(LI $(RELATIVE_LINK2 explicit-conversion, Explicit Conversion Operators))
	$(LI $(RELATIVE_LINK2 char16_t, New Character Types in C++))
	$(LI $(RELATIVE_LINK2 right-angle-brackets, Right Angle Brackets))
	$(LI $(RELATIVE_LINK2 type-deduction, Deducing the type of variable from its initializer expression))
	$(LI $(RELATIVE_LINK2 auto-declarations, The Syntax of auto Declarations))
	$(LI $(RELATIVE_LINK2 inheriting-ctors, Inheriting Constructors))
	$(LI $(RELATIVE_LINK2 sequence-points, A finer-grained alternative to sequence points))
	$(LI $(RELATIVE_LINK2 lambda, (monomorphic) Lambda expressions and closures for C++))
	$(LI $(RELATIVE_LINK2 func, Proposed addition of __func__ predefined identifier from C99))
	$(LI $(RELATIVE_LINK2 atomic, Atomic operations with multi-threaded environments))
	$(LI $(RELATIVE_LINK2 concurrency, Sequencing and the concurrency memory model))
	$(LI $(RELATIVE_LINK2 raw-strings, Raw String Literals))
	$(LI $(RELATIVE_LINK2 pod, PODs unstrung))
	$(LI $(RELATIVE_LINK2 exceptions, Propagating exceptions when joining threads))
	$(LI $(RELATIVE_LINK2 decltype, Decltype))
	$(LI $(RELATIVE_LINK2 sizeof, Extending sizeof))
	$(LI $(RELATIVE_LINK2 utf8-literals, UTF8 Literals))
	$(LI $(RELATIVE_LINK2 ucs-in-literals, Universal Character Names in Literals))
	$(LI $(RELATIVE_LINK2 defaulted, Defaulted and Deleted Functions))
	$(LI $(RELATIVE_LINK2 unions, Unrestricted Unions))
	$(LI $(RELATIVE_LINK2 library, A Multi-threading Library for Standard C++))
	$(LI $(RELATIVE_LINK2 abandoning, Abandoning a Process))
	$(LI $(RELATIVE_LINK2 return-types, New function declaration syntax for deduced return types))
	$(LI $(RELATIVE_LINK2 atomic-signals, Allow atomics use in signal handlers))
	)

	$(UL
	$(LI $(RELATIVE_LINK2 local-classes, Making Local Classes more Useful))
	$(LI $(RELATIVE_LINK2 initializer-lists, Initializer lists))
	$(LI $(RELATIVE_LINK2 thread-local-storage, Thread-Local Storage))
	$(LI $(RELATIVE_LINK2 member-initializers, Member Initializers))
	$(LI $(RELATIVE_LINK2 concepts, Concepts (unified proposal)))
	$(LI $(RELATIVE_LINK2 for-loop, Proposal for new for-loop))
	$(LI $(RELATIVE_LINK2 general-attributes, General Attributes for C++))
	)

	$(UL
	$(LI $(RELATIVE_LINK2 extensible-literals, Extensible Literals))
	$(LI $(RELATIVE_LINK2 dynamic-concurrency, Dynamic initialization and concurrency))
	$(LI $(RELATIVE_LINK2 garbage-collection, Minimal Support for Garbage Collection and Reachability-Based Leak Detection))
	$(LI $(RELATIVE_LINK2 forward-enums, Forward declaration of enumerations))
	)
)

$(SECTION3 $(LNAME2 rvalue-reference, A Proposal to Add an Rvalue Reference to the C++ Language),

	$(P $(LINK2 $(NDOCS)2005/n1770.html, N1770): TBD
	)

)

$(SECTION3 $(LNAME2 class-rvalue, Clarification of Initialization of Class Objects by rvalues),

	$(P $(LINK2 $(NDOCS)2004/n1610.html, N1610): TBD
	)

)

$(SECTION3 $(LNAME2 move-semantics, Extending Move Semantics To *this (Revision 2)),

	$(P $(LINK2 $(NDOCS)2007/n2439.htm, N2439): TBD
	)

)

$(SECTION3 $(LNAME2 static-assert, static_assert),

	$(P $(LINK2 $(NDOCS)2004/n1720.html, N1720):
	$(DDSUBLINK version, StaticAssert, static assert) is
	part of D.
	)

)

$(SECTION3 $(LNAME2 template-aliases, Template aliases for C++),

	$(P $(LINK2 $(NDOCS)2007/n2258.pdf, N2258):
	Both $(LINK2 template.html, templates and template instantiations)
	can be $(DDSUBLINK declaration, alias, aliased):
	)
---
struct S(T) { T int; }
alias X = S;       // alias template
alias Y = S!(int); // alias template instantiation
X!(int) x;
Y y;  // x and y are the same type
---
)

$(SECTION3 $(LNAME2 extern-template, Extern template),

	$(P $(LINK2 $(NDOCS)2006/n1987.htm, N1987):
	This is a workaround for problems in the traditional compile/link
	build model.
	The D compiler deals with this by if multiple modules are compiled
	at the same time, only one instance of a template is generated
	for all the generated object files rather than one instance in each
	object file. Further improvements are planned for generating library
	modules that avoid multiple redundant template instantiations.
	)

)

$(SECTION3 $(LNAME2 variadic-templates, Variadic Templates),

	$(P $(LINK2 $(NDOCS)2007/n2242.pdf, N2242):
	D's $(DDSUBLINK template, variadic-templates, variadic templates).
	)

)

$(SECTION3 $(LNAME2 variadic-template-templates, Extending Variadic Template Template Parameters),

	$(P $(LINK2 $(NDOCS)2008/n2555.pdf, N2555): TBD
	)

)

$(SECTION3 $(LNAME2 nullptr, A name for the null pointer: nullptr),

	$(P $(LINK2 $(NDOCS)2007/n2431.pdf, N2431):
	D has the $(DDSUBLINK expression, null, null) equivalent.
	)

)

$(SECTION3 $(LNAME2 strong-enums, Strongly Typed Enums),

	$(P $(LINK2 $(NDOCS)2007/n2347.pdf, N2347):
	D $(LINK2 enum.html, enums) are:
	)

	$(OL
	$(LI Comparisons between different enum types should be an error,
	but is not:
---
void main()
{
    enum Color { ClrRed, ClrOrange, ClrYellow, ClrGreen, ClrBlue, ClrViolet };
    enum Alert { CndGreen, CndYellow, CndRed };
    Color c = Color.ClrRed;
    Alert a = Alert.CndGreen;
    a = c; // error
    a = Color.ClrYellow; // error
    bool armWeapons = ( a >= Color.ClrYellow ); // ok; oops
}
---
	)
	$(LI The underlying type can be specified.)
	$(LI Named enums are strongly scoped. Anonymous enum members are
	declared in the enclosing scope.)
	$(LI Explicit qualification is needed to specify a named enum
	member.)
	)

)

$(SECTION3 $(LNAME2 extended-friends, Extended friend Declarations),

	$(P $(LINK2 $(NDOCS)2005/n1791.pdf, N1791):
	All code in a module has
	$(DDSUBLINK attribute, ProtectionAttribute, access)
	to private members
	of any struct or class declared in that module that is in
	scope.
	Package protected members can be accessed by any code in the
	same package.
	There is no need in D to have friend declarations or
	complex lookup rules for them.
	)

)

$(SECTION3 $(LNAME2 constant-expressions, Generalized Constant Expressions),

	$(P $(LINK2 $(NDOCS)2007/n2235.pdf, N2235):
	D has $(DDSUBLINK function, interpretation, compile time function execution)
	(CTFE). CTFE is much more flexible, as functions to be evaluated
	at compile time:
	)

	$(OL
	$(LI do not require a special keyword (C++0x requires $(CODE constexpr)))
	$(LI can have multiple statements in the function)
	$(LI can be recursive)
	$(LI can modify local variables)
	$(LI can have out parameters)
	)

)

$(SECTION3 $(LNAME2 namespace-association, Namespace Association ("Strong Using")),

	$(P $(LINK2 $(NDOCS)2008/n2535.html, N2535):
	D doesn't have namespaces,
	so this is irrelevant.
	)

)

$(SECTION3 $(LNAME2 c99-preprocessor, Synchronizing the C++ preprocessor with C99),

	$(P $(LINK2 $(NDOCS)2004/n1653.htm, N1653):
	D does not have a preprocessor,
	so this is not relevant to D.
	)

)

$(SECTION3 $(LNAME2 alignment, Adding Alignment Support to the C++ Programming Language),

	$(P $(LINK2 $(NDOCS)2007/n2341.pdf, N2341):
	D has the $(DDSUBLINK attribute, align, align)
	attribute to specify the alignment
	of declarations, and the $(DDSUBLINK property, alignof, .alignof)
	property to
	determine the alignment size of an expression or type.
	)

)

$(SECTION3 $(LNAME2 conditional, Conditionally-Supported Behavior),

	$(P $(LINK2 $(NDOCS)2004/n1627.pdf, N1627):
	There are some allowed vendor specific behaviors in D,
	such as $(LINK2 pragma.html, pragmas).
	)

)

$(SECTION3 $(LNAME2 undefined-behavior, Changing Undefined Behavior into Diagnosable Errors),

	$(P $(LINK2 $(NDOCS)2004/n1727.pdf, N1727):
	D does not have undefined behavior with integer literal types,
	character escapes, or passing non-POD objects to ellipses.
	)

)

$(SECTION3 $(LNAME2 long-long, Adding the long long type to C++),

	$(P $(LINK2 $(NDOCS)2005/n1811.pdf, N1811):
	D's $(LINK2 type.html, long) type is equivalent.
	)

)

$(SECTION3 $(LNAME2 extended-integer-types, Adding extended integer types to C++),

	$(P $(LINK2 $(NDOCS)2006/n1988.pdf, N1988):
	D has the $(LINK2 type.html, cent and
	ucent) types for
	128 bit integral types (not implemented in dmd or gdc).
	There is no proposal for other extended
	integral types, but it's hard to imagine a justification for
	adding more to the core language.
	)

)

$(SECTION3 $(LNAME2 delegating-ctors, Delegating Constructors),

	$(P $(LINK2 $(NDOCS)2006/n1986.pdf, N1986):
	D has
	$(DDSUBLINK class, delegating-constructors, delegating constructors).
	)

)

$(SECTION3 $(LNAME2 explicit-conversion, Explicit Conversion Operators),

	$(P $(LINK2 $(NDOCS)2007/n2437.html, N2437): TBD
	)

)

$(SECTION3 $(LNAME2 char16_t, New Character Types in C++),

	$(P $(LINK2 $(NDOCS)2007/n2249.html, N2249):
	C++0x adds new character types char16_t and char32_t,
	which are equivalent to D's $(LINK2 type.html, wchar and dchar types).
	The u and U character literal prefixes are equivalent to the
	D $(DDSUBLINK lex, StringLiteral, w and d postfixes).
	)

)

$(SECTION3 $(LNAME2 right-angle-brackets, Right Angle Brackets),

	$(P $(LINK2 $(NDOCS)2005/n1757.html, N1757):
	Since D uses !( ) to instantiate templates rather than
	< >, there are no parsing ambiguities and
	no fixes are necessary.
	)

)

$(SECTION3 $(LNAME2 type-deduction, Deducing the type of variable from its initializer expression),

	$(P $(LINK2 $(NDOCS)2006/n1984.pdf, N1984):
	D has $(DDSUBLINK declaration, AutoDeclaration, type inference)
	from initializers.
	)

)

$(SECTION3 $(LNAME2 auto-declarations, The Syntax of auto Declarations),

	$(P $(LINK2 $(NDOCS)2008/n2546.html, N2546):
	D $(DDSUBLINK attribute, auto, auto declarations)
	do not have syntactic issues.
	)

)

$(SECTION3 $(LNAME2 inheriting-ctors, Inheriting Constructors),

	$(P $(LINK2 $(NDOCS)2008/n2540.html, N2540): TBD
	)

)

$(SECTION3 $(LNAME2 sequence-points, A finer-grained alternative to sequence points),

	$(P $(LINK2 $(NDOCS)2007/n2239.htm, N2239): TBD
	)

)

$(SECTION3 $(LNAME2 lambda, (monomorphic) Lambda expressions and closures for C++),

	$(P $(LINK2 $(NDOCS)2008/n2550.pdf, N2550):
	D has $(GLINK2 expression, FunctionLiteral)s (lambda expressions) and
	$(DDSUBLINK function, closures, closures).
	)

)

$(SECTION3 $(LNAME2 func, Proposed addition of __func__ predefined identifier from C99),

	$(P $(LINK2 $(NDOCS)2007/n2340.html, N2340): TBD
	)

)

$(SECTION3 $(LNAME2 atomic, Atomic operations with multi-threaded environments),

	$(P $(LINK2 $(NDOCS)2007/n2427.html, N2427): TBD
	)

)

$(SECTION3 $(LNAME2 concurrency, Sequencing and the concurrency memory model),

	$(P $(LINK2 $(NDOCS)2007/n2429.htm, N2429): TBD
	)

)

$(SECTION3 $(LNAME2 raw-strings, Raw String Literals),

	$(P $(LINK2 $(NDOCS)2007/n2442.html, N2442):
	D has $(DDSUBLINK lex, StringLiteral, wysiwyg and delimited strings),
	and all strings are Unicode.
	)

)

$(SECTION3 $(LNAME2 pod, PODs unstrung),

	$(P $(LINK2 $(NDOCS)2007/n2294.html, N2294):
	All D $(LINK2 struct.html, structs) are
	$(DDSUBLINK glossary, pod, POD (Plain Old Data)).
	D $(LINK2 class.html, classes) are reference, polymorphic types.
	)

)

$(SECTION3 $(LNAME2 exceptions, Propagating exceptions when joining threads),

	$(P $(LINK2 $(NDOCS)2007/n2179.html, N2179): TBD
	)

)

$(SECTION3 $(LNAME2 decltype, Decltype),

	$(P $(LINK2 $(NDOCS)2007/n2343.pdf, N2343):
	The equivalent D construct is $(DDSUBLINK declaration, typeof, typeof).
	)

)

$(SECTION3 $(LNAME2 sizeof, Extending sizeof),

	$(P $(LINK2 $(NDOCS)2007/n2253.html, N2253):
	Using $(DDSUBLINK property sizeof, sizeof) without a $(I this) object:
---
struct S
{
    int a;
    static int foo()
    {
        return a.sizeof;
    }
}

void test()
{
    int x = S.a.sizeof;
}
---
	works correctly in D.
	)

)

$(SECTION3 $(LNAME2 utf8-literals, UTF-8 Literals),

	$(P $(LINK2 $(NDOCS)2007/n2442.html, N2442):
	$(DDSUBLINK lex, StringLiteral, Char string literals)
	are in UTF-8 format.
	)

)

$(SECTION3 $(LNAME2 ucs-in-literals, Universal Character Names in Literals),

	$(P $(LINK2 $(NDOCS)2007/n2170.html, N2170):
	All Unicode characters are allowed in
	$(DDSUBLINK lex, StringLiteral, string literals).
	Surrogate pair halves are not allowed unless hex literal notation
	is used.
	)

)

$(SECTION3 $(LNAME2 defaulted, Defaulted and Deleted Functions),

	$(P $(DDSUBLINK $(NDOCS)2007/n2326, delete, N2326):
	D alows individual functions to be marked as $(DDSUBLINK attribute, disable, disabled).
	)

)


$(SECTION3 $(LNAME2 unions, Unrestricted Unions),

	$(P $(LINK2 $(NDOCS)2008/n2544.pdf, N2544): TBD
	)

)

$(SECTION3 $(LNAME2 library, A Multi-threading Library for Standard C++),

	$(P $(LINK2 $(NDOCS)2007/n2447.html, N2447): TBD
	)

)

$(SECTION3 $(LNAME2 abandoning, Abandoning a Process),

	$(P $(LINK2 $(NDOCS)2007/n2440.html, N2440): TBD
	)

)

$(SECTION3 $(LNAME2 return-types, New function declaration syntax for deduced return types),

	$(P $(LINK2 $(NDOCS)2007/n2445.html, N2445): TBD
	)

)

$(SECTION3 $(LNAME2 atomic-signals, Allow atomics use in signal handlers),

	$(P $(LINK2 $(NDOCS)2008/n2547.htm, N2547): TBD
	)

)

$(SECTION3 $(LNAME2 local-classes, Making Local Classes more Useful),

	$(P $(LINK2 $(NDOCS)2007/n2402.pdf, N2402):
	D has no restrictions on using local classes as template
	parameters.
	)

)

$(SECTION3 $(LNAME2 initializer-lists, Initializer lists),

	$(P $(LINK2 $(NDOCS)2008/n2531.pdf, N2531):
	D has
	$(DDSUBLINK struct, StructLiteral, struct literals),
	$(DDSUBLINK expression, ArrayLiteral, array literals),
	and $(DDSUBLINK expression, AssocArrayLiteral, associative array literals).
	)

)

$(SECTION3 $(LNAME2 thread-local-storage, Thread-Local Storage),

	$(P $(LINK2 $(NDOCS)2007/n2280.html, N2280):
	Thread-local storage is the default for statics and globals
	in D. Thread-global storage is done by using the
	$(LINK2 migrate-to-shared.html, $(B shared))
	storage class.
	)

)

$(SECTION3 $(LNAME2 member-initializers, Member Initializers),

	$(P $(LINK2 $(NDOCS)2007/n2426.htm, N2426):
	D has
	$(DDSUBLINK class, class-default-initializer, member initializers),
	which are called $(I default initializers).
	)

)

$(SECTION3 $(LNAME2 concepts, Concepts (unified proposal)),

	$(P $(LINK2 $(NDOCS)2006/n2081.pdf, N2081):
	 The D equivalent of C++ concepts are $(LINK2 concepts.html, constraints).
	 (As of $(LINK2 http://www.ddj.com/cpp/218600111, July 2009),
	 Concepts have been dropped from C++0x.)
	)

	$(TABLE2 Concepts and Constraints,

	$(TR
	$(TH Description)
	$(TH D Constraints)
	$(TH C++0x Concepts)
	)

	$(TR
	$(TD Overloading based on concepts/constraints)
	$(TD Yes)
	$(TD Yes)
	)

	$(TR
	$(TD Concepts/constraints on template type parameters)
	$(TD Yes)
	$(TD Yes)
	)

	$(TR
	$(TD Concepts/constraints on template value parameters)
	$(TD Yes)
	$(TD No)
	)

	$(TR
	$(TD Concepts/constraints on template template/alias parameters)
	$(TD Yes)
	$(TD No)
	)

	$(TR
	$(TD Composition and refinement of concepts/constraints)
	$(TD Yes)
	$(TD Yes)
	)

	$(TR
	$(TD Multi-type concepts/constraints)
	$(TD Yes)
	$(TD Yes)
	)

	$(TR
	$(TD Expression of concepts/constraints)
	$(TD Done with compile time expressions)
	$(TD Done by enumeration of function signatures)
	)

	$(TR
	$(TD Axioms)
	$(TD Yes (as static asserts and function preconditions))
	$(TD Yes)
	)

	$(TR
	$(TD new keywords)
	$(TD No)
	$(TD Yes: where, concept, concept_map, axiom, late_check)
	)

	$(TR
	$(TD Semantic analysis of template bodies)
	$(TD Lazy (done at instantiation time))
	$(TD Eager (done at definition time))
	)

	$(TR
	$(TD Template body checked against concept/constraint)
	$(TD No)
	$(TD Yes)
	)

	$(TR
	$(TD Concept maps)
	$(TD No (but could be done with proxy objects))
	$(TD Yes)
	)

	$(TR
	$(TD All operations on constrained types must be specified in
	 concept/constraint)
	$(TD No)
	$(TD Yes)
	)

	$(TR
	$(TD Complexity)
	$(TD $(CODE if (expression)) added to template grammar)
	$(TD quite a bit of new grammar and semantics added)
	)


	)

)

$(SECTION3 $(LNAME2 for-loop, Proposal for new for-loop),

	$(P $(LINK2 $(NDOCS)2007/n2394.html, N2394):
	This is equivalent to the D
	$(DDSUBLINK statement, ForeachRangeStatement, $(I ForeachRangeStatement)).
	)
)

$(SECTION3 $(LNAME2 general-attributes, General Attributes for C++),

	$(P $(LINK2 $(NDOCS)2007/n2418.pdf, N2418):
	Vendor specific attributes can be applied to statements
	and declarations with
	$(LINK2 pragma.html, pragmas).
	)

)

$(SECTION3 $(LNAME2 extensible-literals, Extensible Literals),

	$(P $(LINK2 $(NDOCS)2007/n2378.pdf, N2378):
	D does not have user extensible literals.
	)

)

$(SECTION3 $(LNAME2 dynamic-concurrency, Dynamic initialization and concurrency),

	$(P $(LINK2 $(NDOCS)2008/n2513.html, N2513): TBD
	)

)

$(SECTION3 $(LNAME2 garbage-collection, Minimal Support for Garbage Collection and Reachability-Based Leak Detection),

	$(P $(LINK2 $(NDOCS)2008/n2527.html, N2527):
	Garbage collection is optional in C++0x,
	D $(LINK2 garbage.html, requires it).
	The problem with an optional garbage collector is that in order
	to write general purpose libraries, one must assume that there is
	no garbage collector, therefore none of the productivity enhancing
	advantages of it are available.
	)

)

$(SECTION3 $(LNAME2 forward-enums, Forward declaration of enumerations),

	$(P $(LINK2 $(NDOCS)2008/n2499.pdf, N2499):
	Forward declarations are not necessary in D, as all declarations
	are resolved essentially in parallel.
	Incomplete $(LINK2 enum.html, enum) types, however, are possible:
	)
---
enum E : int;
---
	$(P where the member values are hidden from the user.
	)

)

)

Macros:
	TITLE=D and C++0x
	WIKI=Cpp0x
	DOLLAR=$
	NDOCS=http://www.open-std.org/jtc1/sc22/wg21/docs/papers/
	_=