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Leonidas-from-XIV/foo_broken.ml

Last active June 6, 2018 18:42
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Unifying polymorphic variants
Raw
foo_broken.ml
type foo = [`Hello | `World | `Other]
type bar = [`Yet | `Another | `Other]
type baz = [foo | bar]
type qux = Foo of foo | Bar of bar | Quux
let transform = function
| Foo x -> x
| Bar x -> x
| Quux -> `Other
Raw
foo_compiling_but_ugly.ml
type foo = [`Hello | `World | `Other]
type bar = [`Yet | `Another | `Other]
type baz = [foo | bar]
type qux = Foo of foo | Bar of bar | Quux
let transform = function
| Foo `Hello -> `Hello
| Foo `World -> `World
| Foo `Other -> `Other
| Bar `Yet -> `Yet
| Bar `Another -> `Another
| Bar `Other -> `Other
| Quux -> `Other
Raw
foo_fixed.ml
type foo = [`Hello | `World | `Other]
type bar = [`Yet | `Another | `Other]
type baz = [foo | bar]
type qux = Foo of foo | Bar of bar | Quux
let transform = function
| Foo x -> (x :> baz)
| Bar x -> (x :> baz)
| Quux -> `Other
(* thanks octachron *)
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