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* [Caml-list] Higher-kinded bounded polymorphism
@ 2021-09-13 12:22 Oleg
  2021-09-14 17:03 ` Carette, Jacques
  0 siblings, 1 reply; 2+ messages in thread
From: Oleg @ 2021-09-13 12:22 UTC (permalink / raw)
  To: caml-list


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).

        http://okmij.org/ftp/ML/higher-kind-poly.html

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

The article comes with the complete accompanying code.

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2021-09-13 12:22 [Caml-list] Higher-kinded bounded polymorphism Oleg
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