D模板：对类型列表进行排序

alias Sorted!(4, 2, 1, 3) SortedValues;

module sort;

/*
 * Tango users substitute "tango.core.Tuple" for "std.typetuple" and "Tuple"
 * for "TypeTuple".
 */

import std.typetuple;

struct Val(string v_)
{
    static const v = v_;
}

template Sorted_impl(T)
{
    alias TypeTuple!(T) Sorted_impl;
}

template Sorted_impl(T, U, V...){

    static if( T.v < U.v )
        alias TypeTuple!(T, U, V) Sorted_impl;

    else
        alias TypeTuple!(U, Sorted_impl!(T, V)) Sorted_impl;
}

template Sorted(T)
{
    alias TypeTuple!(T) Sorted;
}

template Sorted(T, U...)
{
    alias Sorted_impl!(T, Sorted_impl!(U)) Sorted;
}

pragma(msg, Sorted!(Val!("a")).stringof);

pragma(msg, Sorted!(Val!("b"), Val!("a")).stringof);

pragma(msg, Sorted!(
    Val!("d"), Val!("a"), Val!("b"), Val!("c")
).stringof);

static assert( false, "nothing to compile here, move along..." );