std.algorithm.remove from array of custom classes?

[Tim K. via Digitalmars-d-learn]

Hi!

I'm trying to remove an item from an array of objects. But I get 
error messages when compiling (see below) which I do not 
understand. I figured I had to override opEquals for it to work, 
but no.
How do I get this to work?

Regards



     class A
     {
         this(string si, uint ui) { s = si; u = ui; }
         string s;
         uint u;

         override bool opEquals(Object obj)
         {
             A o = cast(A)obj;
             return (s == o.s) && (u == o.u);
         }
     }

     int main(string[] argv)
     {
         import std.stdio: writeln;
         import std.algorithm: remove;
         A a = new A("a", 1);
         A b = new A("b", 2);
         A[] as = [a, b];
         as.remove(a);
         writeln(as);

         return 0;
     }


Error:

/usr/include/dmd/phobos/std/algorithm/mutation.d(1503): Error: 
template std.range.primitives.popFrontExactly cannot deduce 
function from argument types !()(A[], A), candidates are:
/usr/include/dmd/phobos/std/range/primitives.d(1791):        
std.range.primitives.popFrontExactly(Range)(ref Range r, size_t 
n) if (isInputRange!Range)
/usr/include/dmd/phobos/std/algorithm/mutation.d(1504): Error: 
template std.range.primitives.popFrontExactly cannot deduce 
function from argument types !()(A[], A), candidates are:
/usr/include/dmd/phobos/std/range/primitives.d(1791):        
std.range.primitives.popFrontExactly(Range)(ref Range r, size_t 
n) if (isInputRange!Range)
/usr/include/dmd/phobos/std/algorithm/mutation.d(1505): Error: 
cannot implicitly convert expression (from) of type dummy.A to 
ulong
dummy.d(21): Error: template instance 
std.algorithm.mutation.remove!(cast(SwapStrategy)2, A[], A) error 
instantiating