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version 2.088.0

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Alias std.meta.AliasSeq

Creates a sequence of zero or more aliases. This is most commonly used as template parameters or arguments.

alias AliasSeq(TList...) = TList;

In previous versions of Phobos, this was known as TypeTuple.

Example

import std.meta;
alias TL = AliasSeq!(int, double);

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

Example

alias TL = AliasSeq!(int, double);

alias Types = AliasSeq!(TL, char);
static assert(is(Types == AliasSeq!(int, double, char)));

Example

Returns an AliasSeq expression of Func being applied to every variadic template argument. 

auto ref ArgCall(alias Func, alias arg)()
{
    return Func(arg);
}

template Map(alias Func, args...)
{
    static if (args.length > 1)
    {
        alias Map = AliasSeq!(ArgCall!(Func, args[0]), Map!(Func, args[1 .. $]));
    }
    else
    {
        alias Map = ArgCall!(Func, args[0]);
    }
}

static int square(int arg)
{
    return arg * arg;
}

static int refSquare(ref int arg)
{
    arg *= arg;
    return arg;
}

static ref int refRetSquare(ref int arg)
{
    arg *= arg;
    return arg;
}

static void test(int a, int b)
{
    writeln(a); // 4
    writeln(b); // 16
}

static void testRef(ref int a, ref int b)
{
    writeln(a++); // 16
    writeln(b++); // 256
}

static int a = 2;
static int b = 4;

test(Map!(square, a, b));

test(Map!(refSquare, a, b));
writeln(a); // 4
writeln(b); // 16

testRef(Map!(refRetSquare, a, b));
writeln(a); // 17
writeln(b); // 257

Authors

Walter Bright, David Nadlinger

License

Boost License 1.0.