[Haskell-cafe] Help finding one-sided ordered list implementation

In "Numerical Representations as Higher-Order Nested Datatypes", Ralf Hinze describes an implementation of one-sided ordered lists as 2-3 search trees under the left spine view. I'm wondering if anyone's actually coded those up somewhere I could download them, or if I'll have to dig into all the details in the paper and write them myself. Thanks, David