each_with_object

static VALUE
enumerator_with_object(VALUE obj, VALUE memo)
{
    struct enumerator *e;
    int argc = 0;
    VALUE *argv = 0;

    RETURN_ENUMERATOR(obj, 1, &memo);
    e = enumerator_ptr(obj);
    if (e->args) {
        argc = RARRAY_LEN(e->args);
        argv = RARRAY_PTR(e->args);
    }
    rb_block_call(e->obj, e->meth, argc, argv,
                  enumerator_with_object_i, memo);

    return memo;
}