Is it possible to define type that enchances record with maybe

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#1

Hello all,

I’m curious if it is possible in purescript to do something like derive type from record that add to all fields maybe, for instance

type Person = { name :: String, age :: Number }

-- Something Person that will result in type { name :: Maybe String, age :: Maybe Number }

Is there way to do that?

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#2

You can template it out with higher-kinded type synonyms.

type PersonFields f =
  ( name :: f String
  , age :: f Number
  )

-- You can pass synonyms like this to other type synonyms
type Unlifted a = a

type Person = { | PersonFields Unlifted }
type PersonMaybe = { | PersonFields Maybe }
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#3

There are more types you can use for f besides Maybe: https://jordanmartinez.github.io/purescript-jordans-reference-site/content/31-Design-Patterns/23-Higher-Kinded-Data.html

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#4

Thank you, thank link is very usefull

1 Like