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. Several templates in this module use or operate on eponymous templates that take a single argument and evaluate to a boolean constant. Such templates are referred to as template predicates. References:Based on ideas in Table 3.1 from Modern C++ Design, Andrei Alexandrescu (Addison-Wesley Professional, 2001) License:
Boost License 1.0. Authors:
Walter Bright, David Nadlinger Source:
std/typetuple.d
- 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 staticIndexOf(T, TList...)
template staticIndexOf(alias 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 %s", staticIndexOf!(long, TypeTuple!(int, long, double))); // prints: The index of long is 1 }
- alias IndexOf = staticIndexOf(T, TList...);
- Kept for backwards compatibility
- template Erase(T, TList...)
template Erase(alias 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...)
template EraseAll(alias 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...)
template Replace(alias T, U, TList...)
template Replace(T, alias U, TList...)
template Replace(alias T, alias 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...)
template ReplaceAll(alias T, U, TList...)
template ReplaceAll(T, alias U, TList...)
template ReplaceAll(alias T, alias 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)
- template staticMap(alias F, T...)
- Evaluates to TypeTuple!(F!(T[0]), F!(T[1]), ..., F!(T[$ - 1])).
Example:
alias staticMap!(Unqual, int, const int, immutable int) T; static assert(is(T == TypeTuple!(int, int, int)));
- template allSatisfy(alias F, T...)
- Tests whether all given items satisfy a template predicate, i.e. evaluates to
F!(T[0]) && F!(T[1]) && ... && F!(T[$ - 1]).
Evaluation is not short-circuited if a false result is encountered; the
template predicate must be instantiable with all the given items.
Example:
static assert(!allSatisfy!(isIntegral, int, double)); static assert(allSatisfy!(isIntegral, int, long));
- template anySatisfy(alias F, T...)
- Tests whether all given items satisfy a template predicate, i.e. evaluates to
F!(T[0]) || F!(T[1]) || ... || F!(T[$ - 1]).
Evaluation is not short-circuited if a true result is encountered; the
template predicate must be instantiable with all the given items.
Example:
static assert(!anySatisfy!(isIntegral, string, double)); static assert(anySatisfy!(isIntegral, int, double));
- template Filter(alias pred, TList...)
- Filters a TypeTuple using a template predicate. Returns a
TypeTuple of the elements which satisfy the predicate.
Examples:
static assert(is(Filter!(isNarrowString, string, wstring, dchar[], char[], dstring, int) == TypeTuple!(string, wstring, char[]))); static assert(is(Filter!(isUnsigned, int, byte, ubyte, dstring, dchar, uint, ulong) == TypeTuple!(ubyte, uint, ulong)));
- template templateNot(alias pred)
- Negates the passed template predicate.
Examples:
alias templateNot!isPointer isNoPointer; static assert(!isNoPointer!(int*)); static assert(allSatisfy!(isNoPointer, string, char, float));
- template templateAnd(Preds...)
- Combines several template predicates using logical AND, i.e. constructs a new
predicate which evaluates to true for a given input T if and only if all of
the passed predicates are true for T.
The predicates are evaluated from left to right, aborting evaluation in a
short-cut manner if a false result is encountered, in which case the latter
instantiations do not need to compile.
Examples:
alias templateAnd!(isNumeric, templateNot!isUnsigned) storesNegativeNumbers; static assert(storesNegativeNumbers!int); static assert(!storesNegativeNumbers!string && !storesNegativeNumbers!uint); // An empty list of predicates always yields true. alias templateAnd!() alwaysTrue; static assert(alwaysTrue!int);
- template templateOr(Preds...)
- Combines several template predicates using logical OR, i.e. constructs a new
predicate which evaluates to true for a given input T if and only at least
one of the passed predicates is true for T.
The predicates are evaluated from left to right, aborting evaluation in a
short-cut manner if a true result is encountered, in which case the latter
instantiations do not need to compile.
Examples:
alias templateOr!(isPointer, isUnsigned) isPtrOrUnsigned; static assert(isPtrOrUnsigned!uint && isPtrOrUnsigned!(short*)); static assert(!isPtrOrUnsigned!int && !isPtrOrUnsigned!string); // An empty list of predicates never yields true. alias templateOr!() alwaysFalse; static assert(!alwaysFalse!int);