stevenfontanella / microlens Goto Github PK

The >>> blah ones.

[here was a list of things, but it's no more]

And that it lets you replace failing in many cases, too. And also that you can do stuff like ([],2,3) ^? (_1.each <> _2 <> _3).

(It was already there, but then I deleted it. I guess I shouldn't have.)

With runnable code and stuff.

• (<$) = set mapped

...and warn in Lens.Micro.Internal about perils of orphan instances (in particular, Ixed, At, and Each shouldn't be used for anything apart from providing additional instances, and it's especially forbidden to export functions with Ixed a =>/etc in the signature).

And write in readme that this way orphan instances aren't that scary anymore.

And remove the “there's no to” bit in the readme.

Some of the package links point to hackage.haskell.com instead of hackage.haskell.org. haskell.com apparently exists but doesn't have to do anything with Haskell the programming language, and it doesn't have a hackage. subdomain.

ageAndCity :: Person :-> (Int, String)
ageAndCity = point $
  (,) <$> fstL >- age
      <*> sndL >- city . place

This example should be replicated in docs.

Should be easy enough. (If anyone wants to do it instead of me, ne's welcome!)

• ekmett/lens@bdc3dc2
• ekmett/lens@5e0b59a
• ekmett/lens@b97b312

https://www.reddit.com/r/haskell/comments/3g22sb/microlens_a_small_lenses_library_with_no/ctuidjx

Look at the type of

Lens s t a b = (a -> f b) -> s -> f t 

pick f = (,) a to get (a -> (a, b)) -> s -> (a, t) and this lets you give back the 'old' value

_2 (\a -> (a, "new value")) (1,2)

If we instead pick f = (,) b

(a -> (b, b)) -> s -> (b, t) 

this lets you give back the 'new' value with something like

_2 (\a -> join (,) (a + 1)) 

Apparently I can find out which modules are marked as unsafe by doing

cabal build --ghc-options "-fwarn-unsafe -fwarn-safe"

https://en.wikibooks.org/wiki/Haskell/Lenses_and_functional_references

Gotta link to it somewhere.

over (ix 1 . ix 1) (+1) [[2,0,0,2],[0,0,0,0],[0,0,0,0],[2,0,0,2]]

gives back th expected result.

But in the absence of preview how does one retrieve the element?

Perhaps this could be the first step towards Lens.Micro being an adequate lens tutorial.

• text
• containers
• unordered-containers
• vector
• array
• bytestring

Additionally, since all these are in the Platform, there could be a package called “microlens-platform” uniting them.

Should add: taking, dropping, element, elementOf.

Done with: failing, filtered, singular.

Write docs for it, and move the conditional import to the beginning.

And check whether it actually is promised in README.

(and add a "please read this tutorial [somewhere else] so that you'd be able to do the Ctrl-Enter thing" warning in bold somewhere on the top)

This would let us not have boring stuff in the docs.

microlens-th doesn't compile with ghc-7.11 as that ships with template-haskell 2.11.