Added pure

[Fresheyeball]

I find myself writing this function alot, perhaps its worth including?

[evancz]

I'd rename it to singleton to be parallel with Dict and Set. I'll add this to the meta issue about core changes.

[evancz]

I'd rename it to singleton to be parallel with Dict and Set. I'll add this to the meta issue about core changes.

[evancz]

The process for adding stuff to core is described here, so we'll go through and think about all these things in a big batch.

[evancz]

The process for adding stuff to core is described here, so we'll go through and think about all these things in a big batch.

[Fresheyeball]

Ok. Fair enough.

[Fresheyeball]

Ok. Fair enough.

[Fresheyeball]

https://github.com/circuithub/elm-list-extra/pull/15 merged

[Fresheyeball]

https://github.com/circuithub/elm-list-extra/pull/15 merged

[evancz]

Can you share an example of when you use it? What kind of code calls for this?

[evancz]

Can you share an example of when you use it? What kind of code calls for this?

[Fresheyeball]

basically I use it in composition chains, for example

https://github.com/Fresheyeball/elm-students/blob/a5ed3ddf557f9a14a2a5f06f0f3d6c171e38ccb2/src/Test.elm#L180

pure : a -> List a
pure x = [x]

test : List H.Html
test = let
  details =
    pure << H.details [ A.style [ ("overflow", "hidden") ] ]
         << (::) (H.summary [] [ H.text "Tests" ])
         << pure << display << quickCheck << suite "Students"
  in details
    [ checkupdate
    , checkMetrics ]

I can find more examples if you need them. Looking back, I use it mostly when making functions that build html.

[Fresheyeball]

basically I use it in composition chains, for example

https://github.com/Fresheyeball/elm-students/blob/a5ed3ddf557f9a14a2a5f06f0f3d6c171e38ccb2/src/Test.elm#L180

pure : a -> List a
pure x = [x]

test : List H.Html
test = let
  details =
    pure << H.details [ A.style [ ("overflow", "hidden") ] ]
         << (::) (H.summary [] [ H.text "Tests" ])
         << pure << display << quickCheck << suite "Students"
  in details
    [ checkupdate
    , checkMetrics ]

I can find more examples if you need them. Looking back, I use it mostly when making functions that build html.

[evancz]

I ask because that's how I'd use it as well, but I was wondering if this is ever nicer code than just naming things. Your example would become:

test : List H.Html
test = let
  toDetails checks =
    H.details
      [ A.style [ ("overflow", "hidden") ] ]
      [ H.summary [] [ H.text "Tests" ]
      , display (quickCheck (suite "Students" checks))
      ]
  in
    [ toDetails
        [ checkUpdate
        , checkMetrics
        ]
    ]

I personally think that is better code. Do you have any other examples?

[evancz]

I ask because that's how I'd use it as well, but I was wondering if this is ever nicer code than just naming things. Your example would become:

test : List H.Html
test = let
  toDetails checks =
    H.details
      [ A.style [ ("overflow", "hidden") ] ]
      [ H.summary [] [ H.text "Tests" ]
      , display (quickCheck (suite "Students" checks))
      ]
  in
    [ toDetails
        [ checkUpdate
        , checkMetrics
        ]
    ]

I personally think that is better code. Do you have any other examples?

[Fresheyeball]

I think you could make a similar criticism of other code using pure, and its fair enough. That said I also find pure useful in development workflow even if I remove it later (which usually happens).

[Fresheyeball]

I think you could make a similar criticism of other code using pure, and its fair enough. That said I also find pure useful in development workflow even if I remove it later (which usually happens).

[evancz]

Okay, thanks for sharing the example, that was very helpful!

[evancz]

Okay, thanks for sharing the example, that was very helpful!

[Fresheyeball]

Cheers!

[Fresheyeball]

Cheers!

[jvoigtlaender]

If I may chime in: There are uses of pure/List.singleton in start-app here and here that are not as easily replaced as exercised for the above example. It seems these are conceptually different uses than the ones you discussed above.

[jvoigtlaender]

If I may chime in: There are uses of pure/List.singleton in start-app here and here that are not as easily replaced as exercised for the above example. It seems these are conceptually different uses than the ones you discussed above.

[Fresheyeball]

While I'm still in favor of List.singleton, it can be easily replaced in start-app:

address =
     Signal.forwardTo messages.address singleton

inputs =
     Signal.mergeMany (messages.signal :: List.map (Signal.map singleton) config.inputs)

vs

address =
     Signal.forwardTo messages.address (\x -> [x])

inputs =
     Signal.mergeMany (messages.signal :: List.map (Signal.map (\x -> [x])) config.inputs)

[Fresheyeball]

While I'm still in favor of List.singleton, it can be easily replaced in start-app:

address =
     Signal.forwardTo messages.address singleton

inputs =
     Signal.mergeMany (messages.signal :: List.map (Signal.map singleton) config.inputs)

vs

address =
     Signal.forwardTo messages.address (\x -> [x])

inputs =
     Signal.mergeMany (messages.signal :: List.map (Signal.map (\x -> [x])) config.inputs)

[jvoigtlaender]

Sure. 😄

Actually, when I wrote that code I defined it as singleton, because I was hoping that at some point List.singleton would be moved from http://package.elm-lang.org/packages/circuithub/elm-list-extra to core, at which time I would come back to this code and use that function.

[jvoigtlaender]

Sure. 😄

Actually, when I wrote that code I defined it as singleton, because I was hoping that at some point List.singleton would be moved from http://package.elm-lang.org/packages/circuithub/elm-list-extra to core, at which time I would come back to this code and use that function.

[jvoigtlaender]

So what I was trying to get at above was that that in these lines we really want singleton to be a function explicitly passed to another function, not inlining it like in the other examples above.

[jvoigtlaender]

So what I was trying to get at above was that that in these lines we really want singleton to be a function explicitly passed to another function, not inlining it like in the other examples above.

[Fresheyeball]

Agreed 👍

[Fresheyeball]

Agreed 👍