Demonstration of template pattern matching

gistfile1.d

// Takes instances of `Foo`

struct Foo(T){ T t; }

string takesFoo(T)(T t) if(is(T == Foo!U, U))
{
	static if(is(T == Foo!U, U))
		return U.stringof;
	else
		static assert(false);
}

immutable foo = takesFoo((Foo!int).init);
static assert(foo == "int");

// Takes any templated type

struct Bar(T, U) {}

string takesAny(T)(T t)
{
	import std.string : format;

	static if(is(T == U!Args, alias U, Args...))
		return "T is %s!%s".format(__traits(identifier, U), Args.stringof);
}


immutable bar = takesAny(Bar!(int, float).init);
static assert(bar == "T is Bar!(int, float)");