import std.stdio;

@property bool empty(T)(T[] a) { return a.length == 0; }
@property ref T front(T)(T[] a) { return a[0]; }
void popFront(T)(ref T[] a) { a = a[1 .. $]; }

R find(R, T)(R haystack, T needle)
    if (is(typeof(haystack.front != needle) == bool))
{    
    while (!haystack.empty && haystack.front != needle)
    {
        haystack.popFront();
    }
    return haystack;
}

unittest
{
    writeln(find([1, 2, 3], 2.0));
    assert(find([1, 2, 3], 1.0));
}