std.meta

Templates to manipulate template parameter sequences (also known as alias sequences).

Some operations on alias sequences are built into the language, such as S[i], which accesses the element at index i in the sequence. S[low .. high] returns a new alias sequence that is a slice of the old one.

For more information, see Compile-time Sequences.

Note: 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.


Category	Templates
Building blocks	Alias AliasSeq aliasSeqOf
Alias sequence filtering	Erase EraseAll Filter NoDuplicates Stride
Alias sequence type hierarchy	DerivedToFront MostDerived
Alias sequence transformation	Repeat Replace ReplaceAll Reverse staticMap staticSort
Alias sequence searching	allSatisfy anySatisfy staticIndexOf
Template predicates	templateAnd templateNot templateOr staticIsSorted
Template instantiation	ApplyLeft ApplyRight Instantiate

References: Based on ideas in Table 3.1 from Modern C++ Design, Andrei Alexandrescu (Addison-Wesley Professional, 2001)

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Aliases

Alias alias Alias(alias a) = a
alias Alias(T) = T: Allows aliasing of any single symbol, type or compile-time expression.
AliasSeq alias AliasSeq(TList...) = TList: Creates a sequence of zero or more aliases. This is most commonly used as template parameters or arguments.
Instantiate alias Instantiate(alias Template, Params...) = Template!Params: Instantiates the given template with the given parameters.

Enums

staticIsSorted eponymoustemplate staticIsSorted(alias cmp, items...): Checks if an AliasSeq is sorted according to cmp.

Templates

ApplyLeft template ApplyLeft(alias Template, args...)
ApplyRight template ApplyRight(alias Template, args...): Partially applies Template by binding its first (left) or last (right) arguments to args.
DerivedToFront template DerivedToFront(TList...): Returns an AliasSeq with the elements of TList sorted so that the most derived types come first.
Erase template Erase(args...): Returns an AliasSeq created from args[1 .. $] with the first occurrence, if any, of args[0] removed.
EraseAll template EraseAll(args...): Returns an AliasSeq created from args[1 .. $] with all occurrences, if any, of args[0] removed.
Filter template Filter(alias pred, args...): Filters an AliasSeq using a template predicate. Returns an AliasSeq of the elements which satisfy the predicate.
MostDerived template MostDerived(T, TList...): Returns the type from TList that is the most derived from type T. If no such type is found, T is returned.
NoDuplicates template NoDuplicates(args...): Returns an AliasSeq created from args with all duplicate types removed.
Repeat template Repeat(size_t n, items...): Creates an AliasSeq which repeats items exactly n times.
Replace 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 an AliasSeq created from TList with the first occurrence of T, if found, replaced with U.
ReplaceAll template ReplaceAll(args...): Returns an AliasSeq created from args[2 .. $] with all occurrences of args[0], if any, replaced with args[1].
Reverse template Reverse(args...): Returns an AliasSeq created from args with the order reversed.
Stride template Stride(int stepSize, Args...): Selects a subset of Args by stepping with fixed stepSize over the sequence. A negative stepSize starts iteration with the last element.
aliasSeqOf template aliasSeqOf(alias iter): Converts any foreach-iterable entity (e.g. an input range) to an alias sequence.
allSatisfy template allSatisfy(alias F, T...): Tests whether all given items satisfy a template predicate, i.e. evaluates to F!(T[0]) && F!(T[1]) && ... && F!(T[$ - 1]).
anySatisfy template anySatisfy(alias F, T...): Tests whether any given items satisfy a template predicate, i.e. evaluates to F!(T[0]) || F!(T[1]) || ... || F!(T[$ - 1]).
staticIndexOf template staticIndexOf(args...): Returns the index of the first occurrence of args[0] in the sequence args[1 .. $]. args may be types or compile-time values. If not found, -1 is returned.
staticMap template staticMap(alias fun, args...): Evaluates to AliasSeq!(fun!(args[0]), fun!(args[1]), ..., fun!(args[$ - 1])).
staticSort template staticSort(alias cmp, items...): Sorts an AliasSeq using cmp.
templateAnd 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.
templateNot template templateNot(alias pred): Negates the passed template predicate.
templateOr 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.

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