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meta.metafunction: Add Enumerate and EnumerateFrom

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Eugen Wissner 2019-01-28 08:22:38 +01:00
parent 0a2798cc96
commit 4566cf7857
1 changed files with 59 additions and 0 deletions
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59
source/tanya/meta/metafunction.d
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@ -1801,3 +1801,62 @@ if (T.length == 2)
static assert(is(Select!(true, int, float) == int));
static assert(is(Select!(false, int, float) == float));
}
/**
* Attaces a numeric index to each element from $(D_PARAM Args).
*
* $(D_PSYMBOL EnumerateFrom) returns a sequence of tuples ($(D_PSYMBOL Pack)s)
* consisting of the index of each element and the element itself.
*
* Params:
* start = Enumeration initial value.
* Args = Enumerated sequence.
*
* See_Also: $(D_PSYMBOL Enumerate).
*/
template EnumerateFrom(size_t start, Args...)
{
static if (Args.length == 0)
{
alias EnumerateFrom = AliasSeq!();
}
else
{
alias EnumerateFrom = AliasSeq!(Pack!(start, Args[0]), EnumerateFrom!(start + 1, Args[1 .. $]));
}
}
///
@nogc nothrow pure @safe unittest
{
static assert(EnumerateFrom!(0, int, uint, bool).length == 3);
}
///
@nogc nothrow pure @safe unittest
{
alias Expected = AliasSeq!(Pack!(cast(size_t) 0, int),
Pack!(cast(size_t) 1, uint));
static assert(is(EnumerateFrom!(0, int, uint) == Expected));
}
/**
* Attaces a numeric index to each element from $(D_PARAM Args).
*
* $(D_PSYMBOL EnumerateFrom) returns a sequence of tuples ($(D_PSYMBOL Pack)s)
* consisting of the index of each element and the element itself.
*
* Params:
* Args = Enumerated sequence.
*
* See_Also: $(D_PSYMBOL EnumerateFrom).
*/
alias Enumerate(Args...) = EnumerateFrom!(0, Args);
///
@nogc nothrow pure @safe unittest
{
alias Expected = AliasSeq!(Pack!(cast(size_t) 0, int),
Pack!(cast(size_t) 1, uint));
static assert(is(Enumerate!(int, uint) == Expected));
}