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Last update Wed Sep 5 11:42:48 2007

# std.typetuple

Templates with which to manipulate type tuples (also known as type lists).
Some operations on type tuples are built in to the language, such as TL[n] which gets the nth type from the type tuple. TL[lwr .. upr] returns a new type list that is a slice of the old one.
References:
Based on ideas in Table 3.1 from Modern C++ Design, Andrei Alexandrescu (Addison-Wesley Professional, 2001)

template TypeTuple(TList...)
  Creates a typetuple out of a sequence of zero or more types.
  Example:

       import std.typetuple;
       alias TypeTuple!(int, double) TL;

       int foo(TL td)  // same as int foo(int, double);
       {
          return td[0] + cast(int)td[1];
       }

  Example:

       TypeTuple!(TL, char)
       // is equivalent to:
       TypeTuple!(int, double, char)

template IndexOf(T,TList...)
  Returns the index of the first occurrence of type T in the sequence of zero or more types TList. If not found, -1 is returned.
  Example:

       import std.typetuple;
       import std.stdio;

       void foo()
       {
          writefln("The index of long is ",
                IndexOf!(long, TypeTuple!(int, long, double)));
          // prints: The index of long is 1
       }

template Erase(T,TList...)
  Returns a typetuple created from TList with the first occurrence, if any, of T removed.
  Example:

       Erase!(long, int, long, double, char)
       // is the same as:
       TypeTuple!(int, double, char)

template EraseAll(T,TList...)
  Returns a typetuple created from TList with the all occurrences, if any, of T removed.
  Example:

       alias TypeTuple!(int, long, long, int) TL;

       EraseAll!(long, TL)
       // is the same as:
       TypeTuple!(int, int)

template NoDuplicates(TList...)
  Returns a typetuple created from TList with the all duplicate types removed.
  Example:

       alias TypeTuple!(int, long, long, int, float) TL;

       NoDuplicates!(TL)
       // is the same as:
       TypeTuple!(int, long, float)

template Replace(T,U,TList...)
  Returns a typetuple created from TList with the first occurrence of type T, if found, replaced with type U.
  Example:

       alias TypeTuple!(int, long, long, int, float) TL;

       Replace!(long, char, TL)
       // is the same as:
       TypeTuple!(int, char, long, int, float)

template ReplaceAll(T,U,TList...)
  Returns a typetuple created from TList with all occurrences of type T, if found, replaced with type U.
  Example:

       alias TypeTuple!(int, long, long, int, float) TL;

       ReplaceAll!(long, char, TL)
       // is the same as:
       TypeTuple!(int, char, char, int, float)

template Reverse(TList...)
  Returns a typetuple created from TList with the order reversed.
  Example:

       alias TypeTuple!(int, long, long, int, float) TL;

       Reverse!(TL)
       // is the same as:
       TypeTuple!(float, int, long, long, int)

template MostDerived(T,TList...)
  Returns the type from TList that is the most derived from type T. If none are found, T is returned.
  Example:

       class A { }
       class B : A { }
       class C : B { }
       alias TypeTuple!(A, C, B) TL;

       MostDerived!(Object, TL) x;  // x is declared as type C

template DerivedToFront(TList...)
  Returns the typetuple TList with the types sorted so that the most derived types come first.
  Example:

       class A { }
       class B : A { }
       class C : B { }
       alias TypeTuple!(A, C, B) TL;

       DerivedToFront!(TL)
       // is the same as:
       TypeTuple!(C, B, A)

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