import std.algorithm;

T[] delegate(T[]) finder(T)(T x)
    if (is(typeof(x == x) == bool))
{
    return delegate(T[] a) { return find(a, x); };
}

unittest
{
    auto d = finder(5);
    assert(d([1, 3, 5, 7, 9]) == [ 5, 7, 9 ]);
    d = finder(10);
    assert(d([1, 3, 5, 7, 9]) == []);
}
