fixing Stream.sample in Elm-0.15

[jvoigtlaender]

The current 0.15 version is broken for situations like this:

main = Varying.map Graphics.Element.show (Varying.fromStream (0,0) s)

s = let v = Mouse.position
    in Stream.sample always v (Stream.fromVarying v)

The output is never updating! That cannot be what is supposed to happen, right?

The commit here fixes this in the way that changes the existing code of Stream.sample the least.

[evancz]

Nice find, thank you for the fix!

I wonder if this pattern of A, B, or both will show up in other places.

[evancz]

Nice find, thank you for the fix!

I wonder if this pattern of A, B, or both will show up in other places.

[jvoigtlaender]

In such situtations, what I'd actually do is to model the thing as (Maybe A, Maybe B) rather than via type SomeOfAB a b = OnlyA a | OnlyB b | Both a b. For the concrete case, doing it like this: jvoigtlaender@f7262c0. There, it simplifies the definition of the sampleUpdate function quite a bit.

The only reason I didn't right away do this in the pull request here is that I wanted it to be the minimal fix (in terms of changed lines and cognitive load).

[jvoigtlaender]

In such situtations, what I'd actually do is to model the thing as (Maybe A, Maybe B) rather than via type SomeOfAB a b = OnlyA a | OnlyB b | Both a b. For the concrete case, doing it like this: jvoigtlaender@f7262c0. There, it simplifies the definition of the sampleUpdate function quite a bit.

The only reason I didn't right away do this in the pull request here is that I wanted it to be the minimal fix (in terms of changed lines and cognitive load).

[evancz]

That looks great to me, do you mind making a PR for that?

I also changed fps to a Stream which I think simplified stuff there, but I may have messed things up.

[evancz]

That looks great to me, do you mind making a PR for that?

I also changed fps to a Stream which I think simplified stuff there, but I may have messed things up.

[jvoigtlaender]

Have added a PR here: https://github.com/elm-lang/core/pull/195.

I'll also try to take a look at the new version of fps separately.

[jvoigtlaender]

Have added a PR here: https://github.com/elm-lang/core/pull/195.

I'll also try to take a look at the new version of fps separately.