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# std.traits

Templates which extract information about types and symbols at compile time.

Category | Templates
--- | ---
Symbol Name traits | fullyQualifiedName moduleName packageName
Function traits | isFunction arity functionAttributes hasFunctionAttributes functionLinkage FunctionTypeOf isSafe isUnsafe isFinal ParameterDefaults ParameterIdentifierTuple ParameterStorageClassTuple Parameters ReturnType SetFunctionAttributes variadicFunctionStyle
Aggregate Type traits | BaseClassesTuple BaseTypeTuple classInstanceAlignment EnumMembers FieldNameTuple Fields hasAliasing hasElaborateAssign hasElaborateCopyConstructor hasElaborateDestructor hasIndirections hasMember hasNested hasUnsharedAliasing InterfacesTuple isInnerClass isNested MemberFunctionsTuple RepresentationTypeTuple TemplateArgsOf TemplateOf TransitiveBaseTypeTuple
Type Conversion | CommonType ImplicitConversionTargets CopyTypeQualifiers CopyConstness isAssignable isCovariantWith isImplicitlyConvertible
SomethingTypeOf | BooleanTypeOf IntegralTypeOf FloatingPointTypeOf NumericTypeOf UnsignedTypeOf SignedTypeOf CharTypeOf StaticArrayTypeOf DynamicArrayTypeOf ArrayTypeOf StringTypeOf AssocArrayTypeOf BuiltinTypeOf
Categories of types | isType isAggregateType isArray isAssociativeArray isAutodecodableString isBasicType isBoolean isBuiltinType isCopyable isDynamicArray isFloatingPoint isIntegral isNarrowString isConvertibleToString isNumeric isPointer isScalarType isSigned isSomeChar isSomeString isStaticArray isUnsigned
Type behaviours | isAbstractClass isAbstractFunction isCallable isDelegate isExpressions isFinalClass isFinalFunction isFunctionPointer isInstanceOf isIterable isMutable isSomeFunction isTypeTuple
General Types | ForeachType KeyType Largest mostNegative OriginalType PointerTarget Signed Unqual Unsigned ValueType Promoted
Misc | mangledName Select select
User-Defined Attributes | hasUDA getUDAs getSymbolsByUDA

License:
Boost License 1.0.
Authors:
Walter Bright, Tomasz Stachowiak (isExpressions), Andrei Alexandrescu, Shin Fujishiro, Robert Clipsham, David Nadlinger, Kenji Hara, Shoichi Kato

Source: std/traits.d

template `MutableOf`(T)
  Add specific qualifier to the given type T.
template `InoutOf`(T)
  Add specific qualifier to the given type T.
template `ConstOf`(T)
  ditto.
template `SharedOf`(T)
  ditto.
template `SharedInoutOf`(T)
  ditto.
template `SharedConstOf`(T)
  ditto.
template `ImmutableOf`(T)
  ditto.
template `packageName`(alias T)
  Get the full package name for the given symbol.
  Examples:

      import std.traits;
      static assert(packageName!packageName == "std");

template `moduleName`(alias T)
  Get the module name (including package) for the given symbol.
  Examples:

      import std.traits;
      static assert(moduleName!moduleName == "std.traits");

template `fullyQualifiedName`(T...) if (T.length == 1)
  Get the fully qualified name of a type or a symbol. Can act as an intelligent type/symbol to string converter.

  Example:

      module myModule;
      struct MyStruct {}
      static assert(fullyQualifiedName!(const MyStruct[]) == "const(myModule.MyStruct[])");

  Examples:

      static assert(fullyQualifiedName!fullyQualifiedName == "std.traits.fullyQualifiedName");

template `ReturnType`(func...) if (func.length == 1 && isCallable!func)
  Get the type of the return value from a function, a pointer to function, a delegate, a struct with an opCall, a pointer to a struct with an opCall, or a class with an opCall. Please note that ref is not part of a type, but the attribute of the function (see template functionAttributes).
  Examples:

      int foo();
      ReturnType!foo x;   // x is declared as int

template `Parameters`(func...) if (func.length == 1 && isCallable!func)
  Get, as a tuple, the types of the parameters to a function, a pointer to function, a delegate, a struct with an opCall, a pointer to a struct with an opCall, or a class with an opCall.
  Examples:

      int foo(int, long);
      void bar(Parameters!foo);      // declares void bar(int, long);
      void abc(Parameters!foo[1]);   // declares void abc(long);

alias `ParameterTypeTuple` = Parameters(func...) if (func.length == 1 && isCallable!func);
  Alternate name for Parameters, kept for legacy compatibility.
template `arity`(alias func) if (isCallable!func && variadicFunctionStyle!func == Variadic.no)
  Returns the number of arguments of function func. `arity` is undefined for variadic functions.
  Examples:

      void foo(){}
      static assert(arity!foo==0);
      void bar(uint){}
      static assert(arity!bar==1);
      void variadicFoo(uint...){}
      static assert(!__traits(compiles, arity!variadicFoo));

enum `ParameterStorageClass`: uint;
template `ParameterStorageClassTuple`(func...) if (func.length == 1 && isCallable!func)
  Returns a tuple consisting of the storage classes of the parameters of a function func.
  Examples:

      alias STC = ParameterStorageClass; // shorten the enum name

      void func(ref int ctx, out real result, real param)
      {
      }
      alias pstc = ParameterStorageClassTuple!func;
      static assert(pstc.length == 3); // three parameters
      static assert(pstc[0] == STC.ref_);
      static assert(pstc[1] == STC.out_);
      static assert(pstc[2] == STC.none);

  `none`
  `scope_`
  `out_`
  `ref_`
  `lazy_`
  `return_`
    These flags can be bitwise OR-ed together to represent complex storage class.
template `ParameterIdentifierTuple`(func...) if (func.length == 1 && isCallable!func)
  Get, as a tuple, the identifiers of the parameters to a function symbol.
  Examples:

      int foo(int num, string name, int);
      static assert([ParameterIdentifierTuple!foo] == ["num", "name", ""]);

template `ParameterDefaults`(func...) if (func.length == 1 && isCallable!func)
  Get, as a tuple, the default value of the parameters to a function symbol. If a parameter doesn't have the default value, void is returned instead.
  Examples:

      int foo(int num, string name = "hello", int[] = [1,2,3], lazy int x = 0);
      static assert(is(ParameterDefaults!foo[0] == void));
      static assert(   ParameterDefaults!foo[1] == "hello");
      static assert(   ParameterDefaults!foo[2] == [1,2,3]);
      static assert(   ParameterDefaults!foo[3] == 0);

alias `ParameterDefaultValueTuple` = ParameterDefaults(func...) if (func.length == 1 && isCallable!func);
  Alternate name for ParameterDefaults, kept for legacy compatibility.
enum `FunctionAttribute`: uint;
template `functionAttributes`(func...) if (func.length == 1 && isCallable!func)
  Returns the `FunctionAttribute` mask for function func.
  See Also:
  hasFunctionAttributes
  Examples:

      import std.traits : functionAttributes, FunctionAttribute;

      alias FA = FunctionAttribute; // shorten the enum name

      real func(real x) pure nothrow @safe
      {
          return x;
      }
      static assert(functionAttributes!func & FA.pure_);
      static assert(functionAttributes!func & FA.safe);
      static assert(!(functionAttributes!func & FA.trusted)); // not @trusted

  `none`
  `pure_`
  `nothrow_`
  `ref_`
  `property`
  `trusted`
  `safe`
  `nogc`
  `system`
  `const_`
  `immutable_`
  `inout_`
  `shared_`
  `return_`
    These flags can be bitwise OR-ed together to represent a complex attribute.
template `hasFunctionAttributes`(args...) if (args.length > 0 && isCallable!(args[0]) && allSatisfy!(isSomeString, typeof(args[1..$])))
  Checks whether a function has the given attributes attached.
  Parameters:

  args | Function to check, followed by a variadic number of function attributes as strings

  Returns:
  true, if the function has the list of attributes attached and false otherwise.
  See Also:
  functionAttributes
  Examples:

      real func(real x) pure nothrow @safe;
      static assert(hasFunctionAttributes!(func, "@safe", "pure"));
      static assert(!hasFunctionAttributes!(func, "@trusted"));

      // for templates attributes are automatically inferred
      bool myFunc(T)(T b)
      {
          return !b;
      }
      static assert(hasFunctionAttributes!(myFunc!bool, "@safe", "pure", "@nogc", "nothrow"));
      static assert(!hasFunctionAttributes!(myFunc!bool, "shared"));

template `isSafe`(alias func) if (isCallable!func)
  `true` if func is @safe or @trusted.
  Examples:

      @safe    int add(int a, int b) {return a+b;}
      @trusted int sub(int a, int b) {return a-b;}
      @system  int mul(int a, int b) {return a*b;}

      static assert( isSafe!add);
      static assert( isSafe!sub);
      static assert(!isSafe!mul);

enum auto `isUnsafe`(alias func);
  `true` if func is @system.
  Examples:

      @safe    int add(int a, int b) {return a+b;}
      @trusted int sub(int a, int b) {return a-b;}
      @system  int mul(int a, int b) {return a*b;}

      static assert(!isUnsafe!add);
      static assert(!isUnsafe!sub);
      static assert( isUnsafe!mul);

template `functionLinkage`(func...) if (func.length == 1 && isCallable!func)
  Returns the calling convention of function as a string.
  Examples:

      extern(D) void Dfunc() {}
      extern(C) void Cfunc() {}
      static assert(functionLinkage!Dfunc == "D");
      static assert(functionLinkage!Cfunc == "C");

      string a = functionLinkage!Dfunc;
      assert(a == "D");

      auto fp = &Cfunc;
      string b = functionLinkage!fp;
      assert(b == "C");

enum `Variadic`: int;
template `variadicFunctionStyle`(func...) if (func.length == 1 && isCallable!func)
  Determines what kind of variadic parameters function has.
  Examples:

      void func() {}
      static assert(variadicFunctionStyle!func == Variadic.no);

      extern(C) int printf(in char*, ...);
      static assert(variadicFunctionStyle!printf == Variadic.c);

  `no`
    Function is not variadic.
  `c`
    Function is a C-style variadic function.
  `d`
    Function is a D-style variadic function, which uses
    _argptr and _arguments.
  `typesafe`
    Function is a `typesafe` variadic function.
template `FunctionTypeOf`(func...) if (func.length == 1 && isCallable!func)
  Get the function type from a callable object func.
  Using builtin typeof on a property function yields the types of the property value, not of the property function itself. Still, `FunctionTypeOf` is able to obtain function types of properties.

  Note: Do not confuse function types with function pointer types; function types are usually used for compile-time reflection purposes.

  Examples:

      class C
      {
          int value() @property { return 0; }
      }
      static assert(is( typeof(C.value) == int ));
      static assert(is( FunctionTypeOf!(C.value) == function ));

template `SetFunctionAttributes`(T, string linkage, uint attrs) if (isFunctionPointer!T || isDelegate!T)
template `SetFunctionAttributes`(T, string linkage, uint attrs) if (is(T == function))
  Constructs a new function or delegate type with the same basic signature as the given one, but different attributes (including linkage).
  This is especially useful for adding/removing attributes to/from types in generic code, where the actual type name cannot be spelt out.
  Parameters:

  T | The base type.
  linkage | The desired linkage of the result type.
  attrs | The desired FunctionAttributes of the result type.

  Examples:

      alias ExternC(T) = SetFunctionAttributes!(T, "C", functionAttributes!T);

      auto assumePure(T)(T t)
          if (isFunctionPointer!T || isDelegate!T)
      {
          enum attrs = functionAttributes!T | FunctionAttribute.pure_;
          return cast(SetFunctionAttributes!(T, functionLinkage!T, attrs)) t;
      }

template `isInnerClass`(T) if (is(T == class))
  Determines whether T is a class nested inside another class and that T.outer is the implicit reference to the outer class (i.e. outer has not been used as a field or method name)
  Parameters:

  T | type to test

  Returns:
  true if T is a class nested inside another, with the conditions described above; false otherwise
  Examples:

      class C
      {
          int outer;
      }
      static assert(!isInnerClass!C);

      class Outer1
      {
          class Inner1 { }
          class Inner2
          {
              int outer;
          }
      }
      static assert(isInnerClass!(Outer1.Inner1));
      static assert(!isInnerClass!(Outer1.Inner2));

      static class Outer2
      {
          static class Inner
          {
              int outer;
          }
      }
      static assert(!isInnerClass!(Outer2.Inner));

template `isNested`(T) if (is(T == class) || is(T == struct) || is(T == union))
  Determines whether T has its own context pointer. T must be either class, struct, or union.
  Examples:

      static struct S { }
      static assert(!isNested!S);

      int i;
      struct NestedStruct { void f() { ++i; } }
      static assert(isNested!NestedStruct);

template `hasNested`(T)
  Determines whether T or any of its representation types have a context pointer.
  Examples:

      static struct S { }

      int i;
      struct NS { void f() { ++i; } }

      static assert(!hasNested!(S[2]));
      static assert(hasNested!(NS[2]));

template `Fields`(T)
  Get as a tuple the types of the fields of a struct, class, or union. This consists of the fields that take up memory space, excluding the hidden fields like the virtual function table pointer or a context pointer for nested types. If T isn't a struct, class, or union returns a tuple with one element T.
  Examples:

      struct S { int x; float y; }
      static assert(is(Fields!S == TypeTuple!(int, float)));

alias `FieldTypeTuple` = Fields(T);
  Alternate name for Fields, kept for legacy compatibility.
template `FieldNameTuple`(T)
  Get as an expression tuple the names of the fields of a struct, class, or union. This consists of the fields that take up memory space, excluding the hidden fields like the virtual function table pointer or a context pointer for nested types. If T isn't a struct, class, or union returns an expression tuple with an empty string.
  Examples:

      struct S { int x; float y; }
      static assert(FieldNameTuple!S == TypeTuple!("x", "y"));
      static assert(FieldNameTuple!int == TypeTuple!"");

template `RepresentationTypeTuple`(T)
  Get the primitive types of the fields of a struct or class, in topological order.
  Examples:

      struct S1 { int a; float b; }
      struct S2 { char[] a; union { S1 b; S1 * c; } }
      alias R = RepresentationTypeTuple!S2;
      assert(R.length == 4
          && is(R[0] == char[]) && is(R[1] == int)
          && is(R[2] == float) && is(R[3] == S1*));

template `hasAliasing`(T...)
  Returns `true` if and only if T's representation includes at least one of the following:
  1. a raw pointer U* and U is not immutable;
  2. an array U[] and U is not immutable;
  3. a reference to a class or interface type C and C is not immutable.
  4. an associative array that is not immutable.
  5. a delegate.
  Examples:

      struct S1 { int a; Object b; }
      struct S2 { string a; }
      struct S3 { int a; immutable Object b; }
      struct S4 { float[3] vals; }
      static assert( hasAliasing!S1);
      static assert(!hasAliasing!S2);
      static assert(!hasAliasing!S3);
      static assert(!hasAliasing!S4);

template `hasIndirections`(T)
  Returns `true` if and only if T's representation includes at least one of the following:
  1. a raw pointer U*;
  2. an array U[];
  3. a reference to a class type C.
  4. an associative array.
  5. a delegate.
  Examples:

      static assert( hasIndirections!(int[string]));
      static assert( hasIndirections!(void delegate()));
      static assert( hasIndirections!(void delegate() immutable));
      static assert( hasIndirections!(immutable(void delegate())));
      static assert( hasIndirections!(immutable(void delegate() immutable)));

      static assert(!hasIndirections!(void function()));
      static assert( hasIndirections!(void*[1]));
      static assert(!hasIndirections!(byte[1]));

template `hasUnsharedAliasing`(T...)
  Returns `true` if and only if T's representation includes at least one of the following:
  1. a raw pointer U* and U is not immutable or shared;
  2. an array U[] and U is not immutable or shared;
  3. a reference to a class type C and C is not immutable or shared.
  4. an associative array that is not immutable or shared.
  5. a delegate that is not shared.
  Examples:

      struct S1 { int a; Object b; }
      struct S2 { string a; }
      struct S3 { int a; immutable Object b; }
      static assert( hasUnsharedAliasing!S1);
      static assert(!hasUnsharedAliasing!S2);
      static assert(!hasUnsharedAliasing!S3);

      struct S4 { int a; shared Object b; }
      struct S5 { char[] a; }
      struct S6 { shared char[] b; }
      struct S7 { float[3] vals; }
      static assert(!hasUnsharedAliasing!S4);
      static assert( hasUnsharedAliasing!S5);
      static assert(!hasUnsharedAliasing!S6);
      static assert(!hasUnsharedAliasing!S7);

template `hasElaborateCopyConstructor`(S)
  True if S or any type embedded directly in the representation of S defines an elaborate copy constructor. Elaborate copy constructors are introduced by defining this(this) for a struct.
  Classes and unions never have elaborate copy constructors.
  Examples:

      static assert(!hasElaborateCopyConstructor!int);

      static struct S1 { }
      static struct S2 { this(this) {} }
      static struct S3 { S2 field; }
      static struct S4 { S3[1] field; }
      static struct S5 { S3[] field; }
      static struct S6 { S3[0] field; }
      static struct S7 { @disable this(); S3 field; }
      static assert(!hasElaborateCopyConstructor!S1);
      static assert( hasElaborateCopyConstructor!S2);
      static assert( hasElaborateCopyConstructor!(immutable S2));
      static assert( hasElaborateCopyConstructor!S3);
      static assert( hasElaborateCopyConstructor!(S3[1]));
      static assert(!hasElaborateCopyConstructor!(S3[0]));
      static assert( hasElaborateCopyConstructor!S4);
      static assert(!hasElaborateCopyConstructor!S5);
      static assert(!hasElaborateCopyConstructor!S6);
      static assert( hasElaborateCopyConstructor!S7);

template `hasElaborateAssign`(S)
  True if S or any type directly embedded in the representation of S defines an elaborate assignment. Elaborate assignments are introduced by defining opAssign(typeof(this)) or opAssign(ref typeof(this)) for a struct or when there is a compiler-generated opAssign.
  A type S gets compiler-generated opAssign in case it has an elaborate copy constructor or elaborate destructor.
  Classes and unions never have elaborate assignments.

  Note: Structs with (possibly nested) postblit operator(s) will have a hidden yet elaborate compiler generated assignment operator (unless explicitly disabled).

  Examples:

      static assert(!hasElaborateAssign!int);

      static struct S  { void opAssign(S) {} }
      static assert( hasElaborateAssign!S);
      static assert(!hasElaborateAssign!(const(S)));

      static struct S1 { void opAssign(ref S1) {} }
      static struct S2 { void opAssign(int) {} }
      static struct S3 { S s; }
      static assert( hasElaborateAssign!S1);
      static assert(!hasElaborateAssign!S2);
      static assert( hasElaborateAssign!S3);
      static assert( hasElaborateAssign!(S3[1]));
      static assert(!hasElaborateAssign!(S3[0]));

template `hasElaborateDestructor`(S)
  True if S or any type directly embedded in the representation of S defines an elaborate destructor. Elaborate destructors are introduced by defining ~this() for a struct.
  Classes and unions never have elaborate destructors, even though classes may define ~this().
  Examples:

      static assert(!hasElaborateDestructor!int);

      static struct S1 { }
      static struct S2 { ~this() {} }
      static struct S3 { S2 field; }
      static struct S4 { S3[1] field; }
      static struct S5 { S3[] field; }
      static struct S6 { S3[0] field; }
      static struct S7 { @disable this(); S3 field; }
      static assert(!hasElaborateDestructor!S1);
      static assert( hasElaborateDestructor!S2);
      static assert( hasElaborateDestructor!(immutable S2));
      static assert( hasElaborateDestructor!S3);
      static assert( hasElaborateDestructor!(S3[1]));
      static assert(!hasElaborateDestructor!(S3[0]));
      static assert( hasElaborateDestructor!S4);
      static assert(!hasElaborateDestructor!S5);
      static assert(!hasElaborateDestructor!S6);
      static assert( hasElaborateDestructor!S7);

enum auto `hasMember`(T, string name);
  Yields `true` if and only if T is an aggregate that defines a symbol called name.
  Examples:

      static assert(!hasMember!(int, "blah"));
      struct S1 { int blah; }
      struct S2 { int blah(){ return 0; } }
      class C1 { int blah; }
      class C2 { int blah(){ return 0; } }
      static assert(hasMember!(S1, "blah"));
      static assert(hasMember!(S2, "blah"));
      static assert(hasMember!(C1, "blah"));
      static assert(hasMember!(C2, "blah"));

template `EnumMembers`(E) if (is(E == enum))
  Retrieves the members of an enumerated type enum E.
  Parameters:

  E | An enumerated type. E may have duplicated values.

  Returns:
  Static tuple composed of the members of the enumerated type E. The members are arranged in the same order as declared in E.

  Note: An enum can have multiple members which have the same value. If you want to use `EnumMembers` to e.g. generate switch cases at compile-time, you should use the std.typetuple.NoDuplicates template to avoid generating duplicate switch cases.

  Note: Returned values are strictly typed with E. Thus, the following code does not work without the explicit cast:

      enum E : int { a, b, c }
      int[] abc = cast(int[]) [ EnumMembers!E ];

  Cast is not necessary if the type of the variable is inferred. See the example below.

  Example: Creating an array of enumerated values:

      enum Sqrts : real
      {
          one   = 1,
          two   = 1.41421,
          three = 1.73205,
      }
      auto sqrts = [ EnumMembers!Sqrts ];
      assert(sqrts == [ Sqrts.one, Sqrts.two, Sqrts.three ]);

  A generic function rank(v) in the following example uses this template for finding a member e in an enumerated type E.

      // Returns i if e is the i-th enumerator of E.
      size_t rank(E)(E e)
          if (is(E == enum))
      {
          foreach (i, member; EnumMembers!E)
          {
              if (e == member)
                  return i;
          }
          assert(0, "Not an enum member");
      }

      enum Mode
      {
          read  = 1,
          write = 2,
          map   = 4,
      }
      assert(rank(Mode.read ) == 0);
      assert(rank(Mode.write) == 1);
      assert(rank(Mode.map  ) == 2);

template `BaseTypeTuple`(A)
  Get a TypeTuple of the base class and base interfaces of this class or interface. `BaseTypeTuple`!Object returns the empty type tuple.
  Examples:

      interface I1 { }
      interface I2 { }
      interface I12 : I1, I2 { }
      static assert(is(BaseTypeTuple!I12 == TypeTuple!(I1, I2)));

      interface I3 : I1 { }
      interface I123 : I1, I2, I3 { }
      static assert(is(BaseTypeTuple!I123 == TypeTuple!(I1, I2, I3)));

template `BaseClassesTuple`(T) if (is(T == class))
  Get a TypeTuple of all base classes of this class, in decreasing order. Interfaces are not included. `BaseClassesTuple`!Object yields the empty type tuple.
  Examples:

      class C1 { }
      class C2 : C1 { }
      class C3 : C2 { }
      static assert(!BaseClassesTuple!Object.length);
      static assert(is(BaseClassesTuple!C1 == TypeTuple!(Object)));
      static assert(is(BaseClassesTuple!C2 == TypeTuple!(C1, Object)));
      static assert(is(BaseClassesTuple!C3 == TypeTuple!(C2, C1, Object)));

template `InterfacesTuple`(T)
  Get a TypeTuple of all interfaces directly or indirectly inherited by this class or interface. Interfaces do not repeat if multiply implemented. `InterfacesTuple`!Object yields the empty type tuple.
template `TransitiveBaseTypeTuple`(T)
  Get a TypeTuple of all base classes of T, in decreasing order, followed by T's interfaces. `TransitiveBaseTypeTuple`!Object yields the empty type tuple.
  Examples:

      interface J1 {}
      interface J2 {}
      class B1 {}
      class B2 : B1, J1, J2 {}
      class B3 : B2, J1 {}
      alias TL = TransitiveBaseTypeTuple!B3;
      assert(TL.length == 5);
      assert(is (TL[0] == B2));
      assert(is (TL[1] == B1));
      assert(is (TL[2] == Object));
      assert(is (TL[3] == J1));
      assert(is (TL[4] == J2));

      assert(TransitiveBaseTypeTuple!Object.length == 0);

template `MemberFunctionsTuple`(C, string name) if (is(C == class) || is(C == interface))
  Returns a tuple of non-static functions with the name name declared in the class or interface C. Covariant duplicates are shrunk into the most derived one.
  Examples:

      interface I { I foo(); }
      class B
      {
          real foo(real v) { return v; }
      }
      class C : B, I
      {
          override C foo() { return this; } // covariant overriding of I.foo()
      }
      alias foos = MemberFunctionsTuple!(C, "foo");
      static assert(foos.length == 2);
      static assert(__traits(isSame, foos[0], C.foo));
      static assert(__traits(isSame, foos[1], B.foo));

template `TemplateOf`(alias T : Base!Args, alias Base, Args...)
template `TemplateOf`(T : Base!Args, alias Base, Args...)
  Returns an alias to the template that T is an instance of.
  Examples:

      struct Foo(T, U) {}
      static assert(__traits(isSame, TemplateOf!(Foo!(int, real)), Foo));

template `TemplateArgsOf`(alias T : Base!Args, alias Base, Args...)
template `TemplateArgsOf`(T : Base!Args, alias Base, Args...)
  Returns a TypeTuple of the template arguments used to instantiate T.
  Examples:

      struct Foo(T, U) {}
      static assert(is(TemplateArgsOf!(Foo!(int, real)) == TypeTuple!(int, real)));

template `classInstanceAlignment`(T) if (is(T == class))
  Returns class instance alignment.
  Examples:

      class A { byte b; }
      class B { long l; }

      // As class instance always has a hidden pointer
      static assert(classInstanceAlignment!A == (void*).alignof);
      static assert(classInstanceAlignment!B == long.alignof);

template `CommonType`(T...)
  Get the type that all types can be implicitly converted to. Useful e.g. in figuring out an array type from a bunch of initializing values. Returns void if passed an empty list, or if the types have no common type.
  Examples:

      alias X = CommonType!(int, long, short);
      assert(is(X == long));
      alias Y = CommonType!(int, char[], short);
      assert(is(Y == void));

template `ImplicitConversionTargets`(T)
  Returns a tuple with all possible target types of an implicit conversion of a value of type T.
  Important note:
  The possible targets are computed more conservatively than the D 2.005 compiler does, eliminating all dangerous conversions. For example, `ImplicitConversionTargets`!double does not include float.
enum bool `isImplicitlyConvertible`(From, To);
  Is From implicitly convertible to To?
  Examples:

      static assert( isImplicitlyConvertible!(immutable(char), char));
      static assert( isImplicitlyConvertible!(const(char), char));
      static assert( isImplicitlyConvertible!(char, wchar));
      static assert(!isImplicitlyConvertible!(wchar, char));

      static assert(!isImplicitlyConvertible!(const(ushort), ubyte));
      static assert(!isImplicitlyConvertible!(const(uint), ubyte));
      static assert(!isImplicitlyConvertible!(const(ulong), ubyte));

      static assert(!isImplicitlyConvertible!(const(char)[], string));
      static assert( isImplicitlyConvertible!(string, const(char)[]));

enum auto `isAssignable`(Lhs, Rhs = Lhs);
  Returns `true` iff a value of type Rhs can be assigned to a variable of type Lhs.
  `isAssignable` returns whether both an lvalue and rvalue can be assigned.
  If you omit Rhs, `isAssignable` will check identity assignable of Lhs.
  Examples:

      static assert( isAssignable!(long, int));
      static assert(!isAssignable!(int, long));
      static assert( isAssignable!(const(char)[], string));
      static assert(!isAssignable!(string, char[]));

      // int is assignable to int
      static assert( isAssignable!int);

      // immutable int is not assignable to immutable int
      static assert(!isAssignable!(immutable int));

template `isCovariantWith`(F, G) if (is(F == function) && is(G == function))
  Determines whether the function type F is covariant with G, i.e., functions of the type F can override ones of the type G.
  Examples:

      interface I { I clone(); }
      interface J { J clone(); }
      class C : I
      {
          override C clone()   // covariant overriding of I.clone()
          {
              return new C;
          }
      }

      // C.clone() can override I.clone(), indeed.
      static assert(isCovariantWith!(typeof(C.clone), typeof(I.clone)));

      // C.clone() can't override J.clone(); the return type C is not implicitly
      // convertible to J.
      static assert(!isCovariantWith!(typeof(C.clone), typeof(J.clone)));

@property T `rvalueOf`(T)(inout __InoutWorkaroundStruct = __InoutWorkaroundStruct.init);
@property ref T `lvalueOf`(T)(inout __InoutWorkaroundStruct = __InoutWorkaroundStruct.init);
  Creates an lvalue or rvalue of type T for typeof(...) and _traits(compiles, ...) purposes. No actual value is returned.

  Note: Trying to use returned value will result in a "Symbol Undefined" error at link time.

  Example:

      // Note that `f` doesn't have to be implemented
      // as is isn't called.
      int f(int);
      bool f(ref int);
      static assert(is(typeof(f(rvalueOf!int)) == int));
      static assert(is(typeof(f(lvalueOf!int)) == bool));

      int i = rvalueOf!int; // error, no actual value is returned

enum bool `isBoolean`(T);
  Detect whether T is a built-in boolean type.
  Examples:

      static assert( isBoolean!bool);
      enum EB : bool { a = true }
      static assert( isBoolean!EB);
      static assert(!isBoolean!(SubTypeOf!bool));

enum bool `isIntegral`(T);
  Detect whether T is a built-in integral type. Types bool, char, wchar, and dchar are not considered integral.
enum bool `isFloatingPoint`(T);
  Detect whether T is a built-in floating point type.
enum bool `isNumeric`(T);
  Detect whether T is a built-in numeric type (integral or floating point).
enum bool `isScalarType`(T);
  Detect whether T is a scalar type (a built-in numeric, character or boolean type).
  Examples:

      static assert(!isScalarType!void);
      static assert( isScalarType!(immutable(int)));
      static assert( isScalarType!(shared(float)));
      static assert( isScalarType!(shared(const bool)));
      static assert( isScalarType!(const(dchar)));

enum bool `isBasicType`(T);
  Detect whether T is a basic type (scalar type or void).
  Examples:

      static assert(isBasicType!void);
      static assert(isBasicType!(const(void)));
      static assert(isBasicType!(shared(void)));
      static assert(isBasicType!(immutable(void)));
      static assert(isBasicType!(shared const(void)));
      static assert(isBasicType!(shared inout(void)));
      static assert(isBasicType!(shared inout const(void)));
      static assert(isBasicType!(inout(void)));
      static assert(isBasicType!(inout const(void)));
      static assert(isBasicType!(immutable(int)));
      static assert(isBasicType!(shared(float)));
      static assert(isBasicType!(shared(const bool)));
      static assert(isBasicType!(const(dchar)));

enum bool `isUnsigned`(T);
  Detect whether T is a built-in unsigned numeric type.
enum bool `isSigned`(T);
  Detect whether T is a built-in signed numeric type.
enum bool `isSomeChar`(T);
  Detect whether T is one of the built-in character types.
  The built-in char types are any of char, wchar or dchar, with or without qualifiers.
  Examples:

      //Char types
      static assert( isSomeChar!char);
      static assert( isSomeChar!wchar);
      static assert( isSomeChar!dchar);
      static assert( isSomeChar!(typeof('c')));
      static assert( isSomeChar!(immutable char));
      static assert( isSomeChar!(const dchar));

      //Non char types
      static assert(!isSomeChar!int);
      static assert(!isSomeChar!byte);
      static assert(!isSomeChar!string);
      static assert(!isSomeChar!wstring);
      static assert(!isSomeChar!dstring);
      static assert(!isSomeChar!(char[4]));

enum bool `isSomeString`(T);
  Detect whether T is one of the built-in string types.
  The built-in string types are Char[], where Char is any of char, wchar or dchar, with or without qualifiers.
  Static arrays of characters (like char[80]) are not considered built-in string types.
  Examples:

      //String types
      static assert( isSomeString!string);
      static assert( isSomeString!(wchar[]));
      static assert( isSomeString!(dchar[]));
      static assert( isSomeString!(typeof("aaa")));
      static assert( isSomeString!(const(char)[]));

      enum ES : string { a = "aaa", b = "bbb" }
      static assert( isSomeString!ES);

      //Non string types
      static assert(!isSomeString!int);
      static assert(!isSomeString!(int[]));
      static assert(!isSomeString!(byte[]));
      static assert(!isSomeString!(typeof(null)));
      static assert(!isSomeString!(char[4]));

enum bool `isNarrowString`(T);
  Detect whether type T is a narrow string.
  All arrays that use char, wchar, and their qualified versions are narrow strings. (Those include string and wstring).
  Examples:

      static assert(isNarrowString!string);
      static assert(isNarrowString!wstring);
      static assert(isNarrowString!(char[]));
      static assert(isNarrowString!(wchar[]));

      static assert(!isNarrowString!dstring);
      static assert(!isNarrowString!(dchar[]));

enum auto `isConvertibleToString`(T);
  Detect whether T is a struct, static array, or enum that is implicitly convertible to a string.
  Examples:

      static struct AliasedString
      {
          string s;
          alias s this;
      }

      enum StringEnum { a = "foo" }

      assert(!isConvertibleToString!string);
      assert(isConvertibleToString!AliasedString);
      assert(isConvertibleToString!StringEnum);
      assert(isConvertibleToString!(char[25]));
      assert(!isConvertibleToString!(char[]));

enum bool `isAutodecodableString`(T);
  Detect whether type T is a string that will be autodecoded.
  All arrays that use char, wchar, and their qualified versions are narrow strings. (Those include string and wstring). Aggregates that implicitly cast to narrow strings are included.
  Parameters:

  T | type to be tested

  Returns:
  `true` if T represents a string that is subject to autodecoding
  See Also: isNarrowString
  Examples:

      static struct Stringish
      {
          string s;
          alias s this;
      }
      assert(isAutodecodableString!wstring);
      assert(isAutodecodableString!Stringish);
      assert(!isAutodecodableString!dstring);

enum bool `isStaticArray`(T);
  Detect whether type T is a static array.
  Examples:

      static assert(!isStaticArray!(const(int)[]));
      static assert(!isStaticArray!(immutable(int)[]));
      static assert(!isStaticArray!(const(int)[4][]));
      static assert(!isStaticArray!(int[]));
      static assert(!isStaticArray!(int[char]));
      static assert(!isStaticArray!(int[1][]));
      static assert(!isStaticArray!(int[int]));
      static assert(!isStaticArray!int);

enum bool `isDynamicArray`(T);
  Detect whether type T is a dynamic array.
  Examples:

      static assert( isDynamicArray!(int[]));
      static assert( isDynamicArray!(string));
      static assert( isDynamicArray!(long[3][]));

      static assert(!isDynamicArray!(int[5]));
      static assert(!isDynamicArray!(typeof(null)));

enum bool `isArray`(T);
  Detect whether type T is an array (static or dynamic; for associative arrays see isAssociativeArray).
  Examples:

      static assert( isArray!(int[]));
      static assert( isArray!(int[5]));
      static assert( isArray!(string));

      static assert(!isArray!uint);
      static assert(!isArray!(uint[uint]));
      static assert(!isArray!(typeof(null)));

enum bool `isAssociativeArray`(T);
  Detect whether T is an associative array type
enum bool `isBuiltinType`(T);
  Detect whether type T is a builtin type.
  Examples:

      class C;
      union U;
      struct S;
      interface I;

      static assert( isBuiltinType!void);
      static assert( isBuiltinType!string);
      static assert( isBuiltinType!(int[]));
      static assert( isBuiltinType!(C[string]));
      static assert(!isBuiltinType!C);
      static assert(!isBuiltinType!U);
      static assert(!isBuiltinType!S);
      static assert(!isBuiltinType!I);
      static assert(!isBuiltinType!(void delegate(int)));

enum bool `isSIMDVector`(T);
  Detect whether type T is a SIMD vector type.
enum bool `isPointer`(T);
  Detect whether type T is a pointer.
template `PointerTarget`(T : T*)
  Returns the target type of a pointer.
enum bool `isAggregateType`(T);
  Detect whether type T is an aggregate type.
  Examples:

      class C;
      union U;
      struct S;
      interface I;

      static assert( isAggregateType!C);
      static assert( isAggregateType!U);
      static assert( isAggregateType!S);
      static assert( isAggregateType!I);
      static assert(!isAggregateType!void);
      static assert(!isAggregateType!string);
      static assert(!isAggregateType!(int[]));
      static assert(!isAggregateType!(C[string]));
      static assert(!isAggregateType!(void delegate(int)));

enum bool `isIterable`(T);
  Returns `true` if T can be iterated over using a foreach loop with a single loop variable of automatically inferred type, regardless of how the foreach loop is implemented. This includes ranges, structs/classes that define opApply with a single loop variable, and builtin dynamic, static and associative arrays.
  Examples:

      struct OpApply
      {
          int opApply(scope int delegate(ref uint) dg) { assert(0); }
      }

      struct Range
      {
          @property uint front() { assert(0); }
          void popFront() { assert(0); }
          enum bool empty = false;
      }

      static assert( isIterable!(uint[]));
      static assert( isIterable!OpApply);
      static assert( isIterable!(uint[string]));
      static assert( isIterable!Range);

      static assert(!isIterable!uint);

enum bool `isMutable`(T);
  Returns `true` if T is not const or immutable. Note that `isMutable` is `true` for string, or immutable(char)[], because the 'head' is mutable.
  Examples:

      static assert( isMutable!int);
      static assert( isMutable!string);
      static assert( isMutable!(shared int));
      static assert( isMutable!(shared const(int)[]));

      static assert(!isMutable!(const int));
      static assert(!isMutable!(inout int));
      static assert(!isMutable!(shared(const int)));
      static assert(!isMutable!(shared(inout int)));
      static assert(!isMutable!(immutable string));

enum bool `isInstanceOf`(alias S, T);
enum auto `isInstanceOf`(alias S, alias T);
  Returns `true` if T is an instance of the template S.
  Examples:

      static struct Foo(T...) { }
      static struct Bar(T...) { }
      static struct Doo(T) { }
      static struct ABC(int x) { }
      static void fun(T)() { }
      template templ(T) { }

      static assert(isInstanceOf!(Foo, Foo!int));
      static assert(!isInstanceOf!(Foo, Bar!int));
      static assert(!isInstanceOf!(Foo, int));
      static assert(isInstanceOf!(Doo, Doo!int));
      static assert(isInstanceOf!(ABC, ABC!1));
      static assert(!isInstanceOf!(Foo, Foo));
      static assert(isInstanceOf!(fun, fun!int));
      static assert(isInstanceOf!(templ, templ!int));

template `isExpressions`(T...)
  Check whether the tuple T is an expression tuple. An expression tuple only contains expressions.
  See Also:
  isTypeTuple.
  Examples:

      static assert(isExpressions!(1, 2.0, "a"));
      static assert(!isExpressions!(int, double, string));
      static assert(!isExpressions!(int, 2.0, "a"));

alias `isExpressionTuple` = isExpressions(T...);
  Alternate name for isExpressions, kept for legacy compatibility.
template `isTypeTuple`(T...)
  Check whether the tuple T is a type tuple. A type tuple only contains types.
  See Also:
  isExpressions.
  Examples:

      static assert(isTypeTuple!(int, float, string));
      static assert(!isTypeTuple!(1, 2.0, "a"));
      static assert(!isTypeTuple!(1, double, string));

template `isFunctionPointer`(T...) if (T.length == 1)
  Detect whether symbol or type T is a function pointer.
  Examples:

      static void foo() {}
      void bar() {}

      auto fpfoo = &foo;
      static assert( isFunctionPointer!fpfoo);
      static assert( isFunctionPointer!(void function()));

      auto dgbar = &bar;
      static assert(!isFunctionPointer!dgbar);
      static assert(!isFunctionPointer!(void delegate()));
      static assert(!isFunctionPointer!foo);
      static assert(!isFunctionPointer!bar);

      static assert( isFunctionPointer!((int a) {}));

template `isDelegate`(T...) if (T.length == 1)
  Detect whether symbol or type T is a delegate.
  Examples:

      static void sfunc() { }
      int x;
      void func() { x++; }

      int delegate() dg;
      assert(isDelegate!dg);
      assert(isDelegate!(int delegate()));
      assert(isDelegate!(typeof(&func)));

      int function() fp;
      assert(!isDelegate!fp);
      assert(!isDelegate!(int function()));
      assert(!isDelegate!(typeof(&sfunc)));

template `isSomeFunction`(T...) if (T.length == 1)
  Detect whether symbol or type T is a function, a function pointer or a delegate.
template `isCallable`(T...) if (T.length == 1)
  Detect whether T is a callable object, which can be called with the function call operator (...).
  Examples:

      interface I { real value() @property; }
      struct S { static int opCall(int) { return 0; } }
      class C { int opCall(int) { return 0; } }
      auto c = new C;

      static assert( isCallable!c);
      static assert( isCallable!S);
      static assert( isCallable!(c.opCall));
      static assert( isCallable!(I.value));
      static assert( isCallable!((int a) { return a; }));

      static assert(!isCallable!I);

template `isAbstractFunction`(T...) if (T.length == 1)
  Detect whether T is a an abstract function.
template `isFinalFunction`(T...) if (T.length == 1)
  Detect whether T is a a final function.
  Examples:

      struct S { void bar() { } }
      final class FC { void foo(); }
      class C
      {
          void bar() { }
          final void foo();
      }
      static assert(!isFinalFunction!(S.bar));
      static assert( isFinalFunction!(FC.foo));
      static assert(!isFinalFunction!(C.bar));
      static assert( isFinalFunction!(C.foo));

enum auto `isNestedFunction`(alias f);
  Determines whether function f requires a context pointer.
template `isAbstractClass`(T...) if (T.length == 1)
  Detect whether T is a an abstract class.
  Examples:

      struct S { }
      class C { }
      abstract class AC { }
      static assert(!isAbstractClass!S);
      static assert(!isAbstractClass!C);
      static assert( isAbstractClass!AC);

template `isFinalClass`(T...) if (T.length == 1)
  Detect whether T is a a final class.
  Examples:

      class C { }
      abstract class AC { }
      final class FC1 : C { }
      final class FC2 { }
      static assert(!isFinalClass!C);
      static assert(!isFinalClass!AC);
      static assert( isFinalClass!FC1);
      static assert( isFinalClass!FC2);

template `Unqual`(T)
  Removes all qualifiers, if any, from type T.
  Examples:

      static assert(is(Unqual!int == int));
      static assert(is(Unqual!(const int) == int));
      static assert(is(Unqual!(immutable int) == int));
      static assert(is(Unqual!(shared int) == int));
      static assert(is(Unqual!(shared(const int)) == int));

template `CopyTypeQualifiers`(FromType, ToType)
  Copies type qualifiers from FromType to ToType.
  Supported type qualifiers:
  - const
  - inout
  - immutable
  - shared
  Examples:

      static assert(is(CopyTypeQualifiers!(inout const real, int) == inout const int));

template `CopyConstness`(FromType, ToType)
  Returns the type of Target with the "constness" of Source. A type's refers to whether it is const, immutable, or inout. If source has no constness, the returned type will be the same as Target.
  Examples:

      const(int) i;
      CopyConstness!(typeof(i), float) f;
      assert( is(typeof(f) == const float));

      CopyConstness!(char, uint) u;
      assert( is(typeof(u) == uint));

      //The 'shared' qualifier will not be copied
      assert(!is(CopyConstness!(shared bool, int) == shared int));

      //But the constness will be
      assert( is(CopyConstness!(shared const real, double) == const double));

      //Careful, const(int)[] is a mutable array of const(int)
      alias MutT = CopyConstness!(const(int)[], int);
      assert(!is(MutT == const(int)));

      //Okay, const(int[]) applies to array and contained ints
      alias CstT = CopyConstness!(const(int[]), int);
      assert( is(CstT == const(int)));

template `ForeachType`(T)
  Returns the inferred type of the loop variable when a variable of type T is iterated over using a foreach loop with a single loop variable and automatically inferred return type. Note that this may not be the same as std.range.ElementType!Range in the case of narrow strings, or if T has both opApply and a range interface.
  Examples:

      static assert(is(ForeachType!(uint[]) == uint));
      static assert(is(ForeachType!string == immutable(char)));
      static assert(is(ForeachType!(string[string]) == string));
      static assert(is(ForeachType!(inout(int)[]) == inout(int)));

template `OriginalType`(T)
  Strips off all enums from type T.
  Examples:

      enum E : real { a }
      enum F : E    { a = E.a }
      alias G = const(F);
      static assert(is(OriginalType!E == real));
      static assert(is(OriginalType!F == real));
      static assert(is(OriginalType!G == const real));

template `KeyType`(V : V[K], K)
  Get the Key type of an Associative Array.
  Examples:

      import std.traits;
      alias Hash = int[string];
      static assert(is(KeyType!Hash == string));
      static assert(is(ValueType!Hash == int));
      KeyType!Hash str = "a"; // str is declared as string
      ValueType!Hash num = 1; // num is declared as int

template `ValueType`(V : V[K], K)
  Get the Value type of an Associative Array.
  Examples:

      import std.traits;
      alias Hash = int[string];
      static assert(is(KeyType!Hash == string));
      static assert(is(ValueType!Hash == int));
      KeyType!Hash str = "a"; // str is declared as string
      ValueType!Hash num = 1; // num is declared as int

template `Unsigned`(T)
  Returns the corresponding unsigned type for T. T must be a numeric integral type, otherwise a compile-time error occurs.
template `Largest`(T...) if (T.length >= 1)
  Returns the largest type, i.e. T such that T.sizeof is the largest. If more than one type is of the same size, the leftmost argument of these in will be returned.
  Examples:

      static assert(is(Largest!(uint, ubyte, ushort, real) == real));
      static assert(is(Largest!(ulong, double) == ulong));
      static assert(is(Largest!(double, ulong) == double));
      static assert(is(Largest!(uint, byte, double, short) == double));
      static if (is(ucent))
          static assert(is(Largest!(uint, ubyte, ucent, ushort) == ucent));

template `Signed`(T)
  Returns the corresponding signed type for T. T must be a numeric integral type, otherwise a compile-time error occurs.
  Examples:

      alias S1 = Signed!uint;
      static assert(is(S1 == int));
      alias S2 = Signed!(const(uint));
      static assert(is(S2 == const(int)));
      alias S3 = Signed!(immutable(uint));
      static assert(is(S3 == immutable(int)));
      static if (is(ucent))
      {
          alias S4 = Signed!ucent;
          static assert(is(S4 == cent));
      }

template `mostNegative`(T) if (isNumeric!T || isSomeChar!T || isBoolean!T)
  Returns the most negative value of the numeric type T.
  Examples:

      static assert(mostNegative!float == -float.max);
      static assert(mostNegative!double == -double.max);
      static assert(mostNegative!real == -real.max);
      static assert(mostNegative!bool == false);

  Examples:

      foreach (T; TypeTuple!(bool, byte, short, int, long))
          static assert(mostNegative!T == T.min);

      foreach (T; TypeTuple!(ubyte, ushort, uint, ulong, char, wchar, dchar))
          static assert(mostNegative!T == 0);

template `Promoted`(T) if (isScalarType!T)
  Get the type that a scalar type T will promote to in multi-term arithmetic expressions.
  Examples:

      ubyte a = 3, b = 5;
      static assert(is(typeof(a * b) == Promoted!ubyte));
      static assert(is(Promoted!ubyte == int));

      static assert(is(Promoted!(shared(bool)) == shared(int)));
      static assert(is(Promoted!(const(int)) == const(int)));
      static assert(is(Promoted!double == double));

template `mangledName`(sth...) if (sth.length == 1)
  Returns the mangled name of symbol or type sth.
  `mangledName` is the same as builtin .mangleof property, except that the correct names of property functions are obtained.

      module test;
      import std.traits : mangledName;

      class C
      {
          int value() @property;
      }
      pragma(msg, C.value.mangleof);      // prints "i"
      pragma(msg, mangledName!(C.value)); // prints "_D4test1C5valueMFNdZi"

template `Select`(bool condition, T...) if (T.length == 2)
  Aliases itself to T[0] if the boolean condition is `true` and to T[1] otherwise.
  Examples:

      // can select types
      static assert(is(Select!(true, int, long) == int));
      static assert(is(Select!(false, int, long) == long));
      static struct Foo {}
      static assert(is(Select!(false, const(int), const(Foo)) == const(Foo)));

      // can select symbols
      int a = 1;
      int b = 2;
      alias selA = Select!(true, a, b);
      alias selB = Select!(false, a, b);
      assert(selA == 1);
      assert(selB == 2);

      // can select (compile-time) expressions
      enum val = Select!(false, -4, 9 - 6);
      static assert(val == 3);

A `select`(bool cond : true, A, B)(A `a`, lazy B `b`);
B `select`(bool cond : false, A, B)(lazy A `a`, B `b`);
  If cond is `true`, returns `a` without evaluating `b`. Otherwise, returns `b` without evaluating `a`.
enum auto `hasUDA`(alias symbol, alias attribute);
  Determine if a symbol has a given user-defined attribute.
  See Also:
  getUDAs
  Examples:

      enum E;
      struct S {}

      @("alpha") int a;
      static assert(hasUDA!(a, "alpha"));
      static assert(!hasUDA!(a, S));
      static assert(!hasUDA!(a, E));

      @(E) int b;
      static assert(!hasUDA!(b, "alpha"));
      static assert(!hasUDA!(b, S));
      static assert(hasUDA!(b, E));

      @E int c;
      static assert(!hasUDA!(c, "alpha"));
      static assert(!hasUDA!(c, S));
      static assert(hasUDA!(c, E));

      @(S, E) int d;
      static assert(!hasUDA!(d, "alpha"));
      static assert(hasUDA!(d, S));
      static assert(hasUDA!(d, E));

      @S int e;
      static assert(!hasUDA!(e, "alpha"));
      static assert(hasUDA!(e, S));
      static assert(!hasUDA!(e, S()));
      static assert(!hasUDA!(e, E));

      @S() int f;
      static assert(!hasUDA!(f, "alpha"));
      static assert(hasUDA!(f, S));
      static assert(hasUDA!(f, S()));
      static assert(!hasUDA!(f, E));

      @(S, E, "alpha") int g;
      static assert(hasUDA!(g, "alpha"));
      static assert(hasUDA!(g, S));
      static assert(hasUDA!(g, E));

      @(100) int h;
      static assert(hasUDA!(h, 100));

      struct Named { string name; }

      @Named("abc") int i;
      static assert(hasUDA!(i, Named));
      static assert(hasUDA!(i, Named("abc")));
      static assert(!hasUDA!(i, Named("def")));

      struct AttrT(T)
      {
          string name;
          T value;
      }

      @AttrT!int("answer", 42) int j;
      static assert(hasUDA!(j, AttrT));
      static assert(hasUDA!(j, AttrT!int));
      static assert(!hasUDA!(j, AttrT!string));

      @AttrT!string("hello", "world") int k;
      static assert(hasUDA!(k, AttrT));
      static assert(!hasUDA!(k, AttrT!int));
      static assert(hasUDA!(k, AttrT!string));

      struct FuncAttr(alias f) { alias func = f; }
      static int fourtyTwo() { return 42; }
      static size_t getLen(string s) { return s.length; }

      @FuncAttr!getLen int l;
      static assert(hasUDA!(l, FuncAttr));
      static assert(!hasUDA!(l, FuncAttr!fourtyTwo));
      static assert(hasUDA!(l, FuncAttr!getLen));
      static assert(!hasUDA!(l, FuncAttr!fourtyTwo()));
      static assert(!hasUDA!(l, FuncAttr!getLen()));

      @FuncAttr!getLen() int m;
      static assert(hasUDA!(m, FuncAttr));
      static assert(!hasUDA!(m, FuncAttr!fourtyTwo));
      static assert(hasUDA!(m, FuncAttr!getLen));
      static assert(!hasUDA!(m, FuncAttr!fourtyTwo()));
      static assert(hasUDA!(m, FuncAttr!getLen()));

template `getUDAs`(alias symbol, alias attribute)
  Gets the matching user-defined attributes from the given symbol.
  If the UDA is a type, then any UDAs of the same type on the symbol will match. If the UDA is a template for a type, then any UDA which is an instantiation of that template will match. And if the UDA is a value, then any UDAs on the symbol which are equal to that value will match.
  See Also:
  hasUDA
  Examples:

      struct Attr
      {
          string name;
          int value;
      }

      @Attr("Answer", 42) int a;
      static assert(getUDAs!(a, Attr).length == 1);
      static assert(getUDAs!(a, Attr)[0].name == "Answer");
      static assert(getUDAs!(a, Attr)[0].value == 42);

      @(Attr("Answer", 42), "string", 9999) int b;
      static assert(getUDAs!(b, Attr).length == 1);
      static assert(getUDAs!(b, Attr)[0].name == "Answer");
      static assert(getUDAs!(b, Attr)[0].value == 42);

      @Attr("Answer", 42) @Attr("Pi", 3) int c;
      static assert(getUDAs!(c, Attr).length == 2);
      static assert(getUDAs!(c, Attr)[0].name == "Answer");
      static assert(getUDAs!(c, Attr)[0].value == 42);
      static assert(getUDAs!(c, Attr)[1].name == "Pi");
      static assert(getUDAs!(c, Attr)[1].value == 3);

      static assert(getUDAs!(c, Attr("Answer", 42)).length == 1);
      static assert(getUDAs!(c, Attr("Answer", 42))[0].name == "Answer");
      static assert(getUDAs!(c, Attr("Answer", 42))[0].value == 42);

      static assert(getUDAs!(c, Attr("Answer", 99)).length == 0);

      struct AttrT(T)
      {
          string name;
          T value;
      }

      @AttrT!uint("Answer", 42) @AttrT!int("Pi", 3) @AttrT int d;
      static assert(getUDAs!(d, AttrT).length == 2);
      static assert(getUDAs!(d, AttrT)[0].name == "Answer");
      static assert(getUDAs!(d, AttrT)[0].value == 42);
      static assert(getUDAs!(d, AttrT)[1].name == "Pi");
      static assert(getUDAs!(d, AttrT)[1].value == 3);

      static assert(getUDAs!(d, AttrT!uint).length == 1);
      static assert(getUDAs!(d, AttrT!uint)[0].name == "Answer");
      static assert(getUDAs!(d, AttrT!uint)[0].value == 42);

      static assert(getUDAs!(d, AttrT!int).length == 1);
      static assert(getUDAs!(d, AttrT!int)[0].name == "Pi");
      static assert(getUDAs!(d, AttrT!int)[0].value == 3);

      struct SimpleAttr {}

      @SimpleAttr int e;
      static assert(getUDAs!(e, SimpleAttr).length == 1);
      static assert(is(getUDAs!(e, SimpleAttr)[0] == SimpleAttr));

      @SimpleAttr() int f;
      static assert(getUDAs!(f, SimpleAttr).length == 1);
      static assert(is(typeof(getUDAs!(f, SimpleAttr)[0]) == SimpleAttr));

      struct FuncAttr(alias f) { alias func = f; }
      static int add42(int v) { return v + 42; }
      static string concat(string l, string r) { return l ~ r; }

      @FuncAttr!add42 int g;
      static assert(getUDAs!(g, FuncAttr).length == 1);
      static assert(getUDAs!(g, FuncAttr)[0].func(5) == 47);

      static assert(getUDAs!(g, FuncAttr!add42).length == 1);
      static assert(getUDAs!(g, FuncAttr!add42)[0].func(5) == 47);

      static assert(getUDAs!(g, FuncAttr!add42()).length == 0);

      static assert(getUDAs!(g, FuncAttr!concat).length == 0);
      static assert(getUDAs!(g, FuncAttr!concat()).length == 0);

      @FuncAttr!add42() int h;
      static assert(getUDAs!(h, FuncAttr).length == 1);
      static assert(getUDAs!(h, FuncAttr)[0].func(5) == 47);

      static assert(getUDAs!(h, FuncAttr!add42).length == 1);
      static assert(getUDAs!(h, FuncAttr!add42)[0].func(5) == 47);

      static assert(getUDAs!(h, FuncAttr!add42()).length == 1);
      static assert(getUDAs!(h, FuncAttr!add42())[0].func(5) == 47);

      static assert(getUDAs!(h, FuncAttr!concat).length == 0);
      static assert(getUDAs!(h, FuncAttr!concat()).length == 0);

      @("alpha") @(42) int i;
      static assert(getUDAs!(i, "alpha").length == 1);
      static assert(getUDAs!(i, "alpha")[0] == "alpha");

      static assert(getUDAs!(i, 42).length == 1);
      static assert(getUDAs!(i, 42)[0] == 42);

      static assert(getUDAs!(i, 'c').length == 0);

template `getSymbolsByUDA`(alias symbol, alias attribute)
  Gets all symbols within symbol that have the given user-defined attribute. This is not recursive; it will not search for symbols within symbols such as nested structs or unions.
  Examples:

      enum Attr;

      static struct A
      {
          @Attr int a;
          int b;
          @Attr void doStuff() {}
          void doOtherStuff() {}
          static struct Inner
          {
              // Not found by getSymbolsByUDA
              @Attr int c;
          }
      }

      // Finds both variables and functions with the attribute, but
      // doesn't include the variables and functions without it.
      static assert(getSymbolsByUDA!(A, Attr).length == 2);
      // Can access attributes on the symbols returned by getSymbolsByUDA.
      static assert(hasUDA!(getSymbolsByUDA!(A, Attr)[0], Attr));
      static assert(hasUDA!(getSymbolsByUDA!(A, Attr)[1], Attr));

      static struct UDA { string name; }

      static struct B
      {
          @UDA("X")
          int x;
          @UDA("Y")
          int y;
          @(100)
          int z;
      }

      // Finds both UDA attributes.
      static assert(getSymbolsByUDA!(B, UDA).length == 2);
      // Finds one `100` attribute.
      static assert(getSymbolsByUDA!(B, 100).length == 1);
      // Can get the value of the UDA from the return value
      static assert(getUDAs!(getSymbolsByUDA!(B, UDA)[0], UDA)[0].name == "X");

      @UDA("A")
      static struct C
      {
          @UDA("B")
          int d;
      }

      // Also checks the symbol itself
      static assert(getSymbolsByUDA!(C, UDA).length == 2);
      static assert(getSymbolsByUDA!(C, UDA)[0].stringof == "C");
      static assert(getSymbolsByUDA!(C, UDA)[1].stringof == "d");

      static struct D
      {
          int x;
      }

      //Finds nothing if there is no member with specific UDA
      static assert(getSymbolsByUDA!(D,UDA).length == 0);

template `allSameType`(T...)
  Returns:
  `true` iff all types T are the same.
  Examples:

      static assert(allSameType!(int, int));
      static assert(allSameType!(int, int, int));
      static assert(allSameType!(float, float, float));
      static assert(!allSameType!(int, double));
      static assert(!allSameType!(int, float, double));
      static assert(!allSameType!(int, float, double, real));
      static assert(!allSameType!(short, int, float, double, real));

enum auto `ifTestable`(T, alias pred = (a) => a);
  Returns:
  `true` iff the type T can be tested in an if-expression, that is if if (pred(T.init)) {} is compilable.
template `isType`(X...) if (X.length == 1)
  Detect whether X is a type. Analogous to is(X). This is useful when used in conjunction with other templates, e.g. allSatisfy!(`isType`, X).
  Returns:
  true if X is a type, false otherwise
  Examples:

      struct S {
          template Test() {}
      }
      class C {}
      interface I {}
      union U {}
      static assert(isType!int);
      static assert(isType!string);
      static assert(isType!(int[int]));
      static assert(isType!S);
      static assert(isType!C);
      static assert(isType!I);
      static assert(isType!U);

      int n;
      void func(){}
      static assert(!isType!n);
      static assert(!isType!func);
      static assert(!isType!(S.Test));
      static assert(!isType!(S.Test!()));

template `isFunction`(X...) if (X.length == 1)
  Detect whether symbol or type X is a function. This is different that finding if a symbol is callable or satisfying is(X == function), it finds specifically if the symbol represents a normal function declaration, i.e. not a delegate or a function pointer.
  Returns:
  true if X is a function, false otherwise
  See Also:
  Use isFunctionPointer or isDelegate for detecting those types respectively.
  Examples:

      static void func(){}
      static assert(isFunction!func);

      struct S
      {
          void func(){}
      }
      static assert(isFunction!(S.func));

template `isFinal`(X...) if (X.length == 1)
  Detect whether X is a final method or class.
  Returns:
  true if X is final, false otherwise
  Examples:

      class C
      {
          void nf() {}
          static void sf() {}
          final void ff() {}
      }
      final class FC { }

      static assert(!isFinal!(C));
      static assert( isFinal!(FC));

      static assert(!isFinal!(C.nf));
      static assert(!isFinal!(C.sf));
      static assert( isFinal!(C.ff));

enum auto `isCopyable`(S);
  Determines whether the type S can be copied. If a type cannot be copied, then code such as MyStruct x; auto y = x; will fail to compile. Copying for structs can be disabled by using @disable this(this).
  Parameters:

  S | The type to check.

  Returns:
  true if S can be copied. false otherwise.
  Examples:

      struct S1 {}                        // Fine. Can be copied
      struct S2 {         this(this) {}}  // Fine. Can be copied
      struct S3 {@disable this(this) {}}  // Not fine. Copying is disabled.
      struct S4 {S3 s;}                   // Not fine. A field has copying disabled.

      class C1 {}

      static assert( isCopyable!S1);
      static assert( isCopyable!S2);
      static assert(!isCopyable!S3);
      static assert(!isCopyable!S4);

      static assert(isCopyable!C1);
      static assert(isCopyable!int);

Copyright Digital Mars 2005 - 2009. | Page generated by Ddoc on Thu Feb 16 13:40:04 2017