Please add `apply` and `pure` to Json.Decode

[jasonzoladz]

It would be nice to have pure and apply defined in Json.Decode, as it seems way more natural than object6. (And it saves the boilerplate of defining them every time.)

I assume (perhaps wrongly?) that they have not been included due to accessibility concerns. (Obviously, you need not discuss Applicatives.) Since the language supports partial application and ADTs, isn't the pedagogy simply:

"pure takes a function/value and puts it a box. apply takes a function in a box, and a value in a box, and returns a value in a box." What am I missing?

[evancz]

The equivalent of pure already exists and is called succeed. I felt that the name pure actively misleads people about what is happening.

Adding the equivalent of apply is planned. In the meantime, these are the guidelines for adding stuff like this and I suspect there's already a *-extras package out there that has it.

Furthermore, it should be pretty easy to define in terms of andThen.

andMap : Decoder (a -> b) -> Decoder a -> Decoder b
andMap decodeFunc decodeValue =
    decodeFunc `andThen` \func -> decodeVaue `andThen` \value -> succeed (func value)

[evancz]

The equivalent of pure already exists and is called succeed. I felt that the name pure actively misleads people about what is happening.

Adding the equivalent of apply is planned. In the meantime, these are the guidelines for adding stuff like this and I suspect there's already a *-extras package out there that has it.

Furthermore, it should be pretty easy to define in terms of andThen.

andMap : Decoder (a -> b) -> Decoder a -> Decoder b
andMap decodeFunc decodeValue =
    decodeFunc `andThen` \func -> decodeVaue `andThen` \value -> succeed (func value)

[jasonzoladz]

I know that it's easily defined:
apply = object2 (<|)

My point was that it's a foundational primitive that is trivial to add to the library.

[jasonzoladz]

I know that it's easily defined:
apply = object2 (<|)

My point was that it's a foundational primitive that is trivial to add to the library.

[evancz]

Adding the equivalent of apply is planned. In the meantime...

It is very hard to respond to the volume of API suggestions for core in a piecemeal way. Adding 100 trivial things to core is not a trivial thing, especially if you care about how all those things work together conceptually across all the different packages. Adding something like apply is planned. It wasn't in the first version, but many folks have wanted it since then. So it's in the plan to add it.

[evancz]

Adding the equivalent of apply is planned. In the meantime...

It is very hard to respond to the volume of API suggestions for core in a piecemeal way. Adding 100 trivial things to core is not a trivial thing, especially if you care about how all those things work together conceptually across all the different packages. Adding something like apply is planned. It wasn't in the first version, but many folks have wanted it since then. So it's in the plan to add it.

[jasonzoladz]

Thanks Evan. I appreciate the reply.

On Tuesday, September 29, 2015, Evan Czaplicki notifications@github.com
wrote:

Adding the equivalent of apply is planned. In the meantime...

It is very hard to respond to the volume of API suggestions for core in a
piecemeal way. This is planned. It wasn't in the first version, but many
folks have wanted it since then. So it's in the plan to add it.

—
Reply to this email directly or view it on GitHub
https://github.com/elm-lang/core/issues/416#issuecomment-144222334.

[jasonzoladz]

Thanks Evan. I appreciate the reply.

On Tuesday, September 29, 2015, Evan Czaplicki notifications@github.com
wrote:

Adding the equivalent of apply is planned. In the meantime...

It is very hard to respond to the volume of API suggestions for core in a
piecemeal way. This is planned. It wasn't in the first version, but many
folks have wanted it since then. So it's in the plan to add it.

—
Reply to this email directly or view it on GitHub
https://github.com/elm-lang/core/issues/416#issuecomment-144222334.