[mercury-users] overlapping instance declarations

[Michael Day]

<interesting commentary on type class semantics>

> This is a very direct, very simple way of specifying the declarative
> and operational semantics of code using type classes.

Must the semantics of type classes be specified in a way that does not
involve transformation, such as adding higher order arguments to
predicates that take a type class constrained variable as input and so
forth?

If so, then it would seem very difficult to specify the semantics of type
classes with module qualified instances, which require an explicit
connection from the point at which a value was passed in and the point at
which a particular type class method was called.

Michael

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