November 15, 2011
Pure Subtype Systems

I stumbled across this while looking for solutions to the expression problem:

Pure Subtype Systems: A Type Theory for Extensible Software [PDF] by DeLesley Hutchins, 2009.

Hutchins bases his type theory on subtyping rather than typing.

As far as the expression problem goes, one solution is to support late-binding for types.  The author points to the gbeta programming language, which supports this feature.

Of the solutions I’ve seen, I think this is probably the best.  Besides actually solving the problem, it also has the benefit of being easy to understand.

November 11, 2011
Multiple Inheritance Without Diamonds

Here’s an interesting solution to the diamond problem:

CZ: Multiple Inheritance Without Diamonds [PDF] by Donna Malayeri, 2009.

The “requires” construct looks nice.

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