How do I combine lenses which contain context?

Question

I'm starting from authorityL via authorityHostL to hostBSL - I know you can combine lenses via

(authorityL . authorityHostL . hostBSL)

but that fails with Couldn't match type ‘Authority’ with ‘Maybe Authority’. How do I properly deal with the Maybe here?

Does simply adding `_Just` in between help? I can't test it currently unfortunately. — Christoph Hegemann, Feb 02 '17 at 12:32
Yeah. `(authorityL .> _Just .> authorityHostL .> hostBSL)` works. — Reactormonk, Feb 02 '17 at 12:37
@ChristophHegemann You should probably post that as an answer. — jkeuhlen, Feb 02 '17 at 15:35

score 0 · Accepted Answer · answered Feb 03 '17 at 09:23

0

You can add a _Just in between to only focus in on the successful results.

(authorityL . _Just . authorityHostL . hostBSL)

does the trick like it's said in the comments.

answered Feb 03 '17 at 09:23

1 Answers1