Operator cheatsheet

[minad]

Hi,

I like the minimal dependency approach of microlens, since I just started to use a lens library in Haskell. But I am wondering how you decide which operators to include and which not. For example I am missing ?=, which I expected to be there for consistency with ?~. It would also be great to have a complete list of all operators which shows if the operator exists in lens or microlens. Maybe you already have that written down somewhere since you derived the microlens design from lens?

And thx for the library!

[minad]

I know https://github.com/ekmett/lens/wiki/Operators, but it seems very incomplete. To find these many small functions I usually find the haddock documentation to scattered. Any recommendations?

[neongreen]

But I am wondering how you decide which operators to include and which not.

Pretty much on an ad-hoc basis (when I or someone else needs something, I add it). For the same reason there is mapAccumLOf but no other *Of functions.

I don't like this approach, but at the same time I think it's the least of three evils (the other evils being “keep it consistent and small, refuse to make exceptions to satisfy actual users' needs” and “add things that users need, but also add lots of things that haven't been requested in order to preserve consistency” – the thing is that when there are several symmetrical functions/operators, it does not mean that they are used approximately as often).

I will add ?= and make a release shortly (or you can add it by yourself, it's not hard!).

Regarding operator cheatsheets: I'm not aware of any that would include ?= (which is kinda surprising). I should make one.

[neongreen]

There'll be one at guide.aelve.com (see aelve/guide#101) at some point in the future; I'll ping you when it's done.

[minad]

good idea with guide. looking forward to it!

[neongreen]

Released microlens-mtl-0.1.9.

[minad]

👍 thx

[neongreen]

Hey, this issue ain't going nowhere until I've actually made a cheatsheet :)

[minad]

Cool. Nice to know there is still activity. But I have to admit that I switched to lens by now.

[tebello-thejane]

Hmm...

Just as a quick anecdote, I very recently encountered this "issue" when moving pretty-simple from lens to microlens.

I have no idea what the <>= operator is supposed to do, exactly, but I was able to replace it by reading the lens source code. That is, microlens, even with its lack of prisms and such, could have included this operator with minimal fuss. I feel that lens contains a bit too many convenience functions and instances, and this, coupled with sometimes paltry documentation, makes the package a bit less usable than it should be.

So I'm all for only including those operators which users have asked for.

This is not a request for the inclusion of the <>= operator, though. ;-)