If I want to extend List with additional functions, I can just do: include module type of List val flat_map : ('a -> 'b list) -> 'a list -> 'b list include List let flat_map f l = flatten (map f) l and that’s fine. But if I want to extend Format, this simple trick doesn’t work so well, because t…

Easy peasy! There is an OCaml idiom for that: include module type of struct include Format end To understand why that works, you need a bit of knowledge on the module type system. The basic idea is the following: the struct include X end dance forces the typechecker to “strengthen” the module sign…

Extend existing module

Learning

yawaramin January 4, 2018, 11:56pm 2

Note that using module type of may lead to versioning difficulties and possible breakage: Serious OPAM package quality issues

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Extend existing module

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