[Haskell-cafe] A model theory question

[Patrick Browne]

Hi,
Below is an assumption (which could be wrong) and two questions.

ASSUMPTION 1
Only smaller models can be specified using the sub-class mechanism.
For example if we directly make a subclass A => B then every instance of
B must also be an instance of A (B implies A or B is a subset of A).
Hence, type classes cannot be combined using sub-classing to provide
specifications of bigger models.

QUESTIONS
1) If assumption 1 is correct, is there a mechanism whereby the module
system can be used to construct bigger models?

2) If there is such a mechanism does it involve type classes or is it a
module only solution?



Regards,
Pat

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