Here's my solution. Note quite as cool as FeepingCreature's, but probably simpler to understand; it works by recursively inserting the first type into the rest of the list (after having sorting it).
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..." );