Using traversals in L.pick about partial.lenses

[polytypic]

In case you only want a unidirectional operation, you can freely compose optics with functions. So, you could say (playground):

L.get(
  L.pick({
    stuff: L.collect(['a', L.elems, L.props('b')]),
    otherStuff: ['d', 'e']
  }),
  data)

Above L.collect(...) results in an ordinary function that will be used as a read-only optic.

The company example uses the above technique in one half of the joinView isomorphism constructor.

BTW, the Gitter channel is also good for questions like this.

[elysion]

Oh, did not realize I could use functions like that or use Gitter. Using functions in the lenses do solve the problems I currently have as I do not need to use the lense in the other direction. Being able to use the traversals with pick in both directions sounds like something that could be useful in other cases.

[polytypic]

I just realized that there is likely a better way to handle this case. What you are actually looking for here is a kind of adapter between two forms of the same data. We can express that using isomorphisms. Here is a playground that does just that. In this case the adapter is lossy, but notice that the adapter works in both directions. I'll add the array iso constructor to the library when I have a moment.