Proposal: Add singleton function to Data.List module
taylor at fausak.me
Mon Aug 12 16:14:37 UTC 2019
I originally made this suggestion on GitLab, but I was told to make it here instead.
# Add list singleton function
Sometimes it is convenient to have a function to wrap an element in a list. There are many ways to do this already, but none of them are as clear as a separate monomorphic function.
- `pure`: Polymorphic, works for any `Functor`.
- `pure @`: Noisy, requires `-XTypeApplications`.
- `(: )`: Subjectively ugly.
- `(\x -> [x])`: Syntactically noisy.
This Twitter thread includes some additional commentary: https://twitter.com/taylorfausak/status/1159264862247280640
I would like to add a `singleton` function to `Data.List` that mirrors the `singleton` function for other containers: https://www.stackage.org/lts-14.0/hoogle?q=singleton
singleton :: a -> [a]
singleton x = [x]
Other Haskell-like languages include this function:
- PureScript: https://pursuit.purescript.org/packages/purescript-lists/5.4.0/docs/Data.List#v:singleton
- Elm: https://package.elm-lang.org/packages/elm/core/latest/List#singleton
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