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From: Oleg <>
Subject: [Caml-list] Higher-kinded bounded polymorphism
Date: Mon, 13 Sep 2021 21:21:39 +0900
Message-ID: <20210913122139.GA3696@Melchior.localnet> (raw)

Abstraction over polymorphic types is something that one comes across
from time to time, especially when implementing operations generic
over collections, or embedding typed DSLs (particularly in
tagless-final style). One immediately learns that OCaml does not have
higher-kinded type variables (type variables that range over type
constructors like list and array); does not permit type constructors
appearing by themselves, without being applied to the right number of
arguments; and restricts polymorphic types in other ways (e.g., not
allowing them in type constraints of package types). One soon learns
that the module system (using functors) is a way to realize
higher-kinded polymorphism in OCaml. It takes longer to learn it is
not the only way, however.

The following web page is written to speed up this learning. It
collects what I have learned and rediscovered on this topic, arranged
into a single story and with new explanations and attributions (and
occasionally, new variations).

One interesting discovery is that some problems that ostensibly
require higher-kinded polymorphism really do not.

The article comes with the complete accompanying code.

             reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-13 12:22 Oleg [this message]
2021-09-14 17:03 ` Carette, Jacques

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