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> I.e. they can filter among many fields to set, then modify multiple fields at once, and so on. These generalizations are usually referred to as "optics", wit

> I.e. they can filter among many fields to set, then modify multiple fields at once, and so on. These generalizations are usually referred to as "optics", with "lenses" reserved for the single-target case.

kqr 4y ago
Yet ekmetts package is called "lens" and not "optic". While I agree with you in principle, I think that ship has sailed and for all practical purposes, "lenses" has come to mean both the narrower definition that is arguably correct, and optics more generally. It's a historical accident, much like a lot of people use "function" to mean all sorts of subprogram, including procedures and sometimes even methods!
nerdponx 4y ago
I would love to see some kind of table or diagram that shows all the various "optics" in some kind of structured format. Lenses are the only one that I can keep straight in my head.
- endgame 4y ago
  https://raw.githubusercontent.com/wiki/ekmett/lens/images/Hierarchy.png https://raw.githubusercontent.com/wiki/ekmett/lens/images/Hi... If you need to find it again, it shows up in the README which is in the github repo and the page on Hackage.
- hither_shores 4y ago
  There are infinitely many, so all is out, but the standard ones are covered here: https://oleg.fi/gists/posts/2017-04-18-glassery.html https://oleg.fi/gists/posts/2017-04-18-glassery.html Page 10 of this paper has a table with references to some more exotic optics, though it's going to be hard to parse without some category theory: https://arxiv.org/pdf/2001.07488.pdf https://arxiv.org/pdf/2001.07488.pdf
- Tarean 4y ago
  The optics library is a bit stricter, using separate types with implicit conversions to give better type errors, and the subtyping diagram is here https://hackage.haskell.org/package/optics-0.4.2/docs/Optics.html#g:3 https://hackage.haskell.org/package/optics-0.4.2/docs/Optics... The lens documentation has this diagram https://i.imgur.com/ALlbPRa.png https://i.imgur.com/ALlbPRa.png These both skip over indexed versions, and some niche optics like grates aren't in the libraries yet afaik

kqr 4y ago

Yet ekmetts package is called "lens" and not "optic". While I agree with you in principle, I think that ship has sailed and for all practical purposes, "lenses" has come to mean both the narrower definition that is arguably correct, and optics more generally. It's a historical accident, much like a lot of people use "function" to mean all sorts of subprogram, including procedures and sometimes even methods!

nerdponx 4y ago

I would love to see some kind of table or diagram that shows all the various "optics" in some kind of structured format. Lenses are the only one that I can keep straight in my head.

endgame 4y ago
https://raw.githubusercontent.com/wiki/ekmett/lens/images/Hierarchy.png https://raw.githubusercontent.com/wiki/ekmett/lens/images/Hi... If you need to find it again, it shows up in the README which is in the github repo and the page on Hackage.
hither_shores 4y ago
There are infinitely many, so all is out, but the standard ones are covered here: https://oleg.fi/gists/posts/2017-04-18-glassery.html https://oleg.fi/gists/posts/2017-04-18-glassery.html Page 10 of this paper has a table with references to some more exotic optics, though it's going to be hard to parse without some category theory: https://arxiv.org/pdf/2001.07488.pdf https://arxiv.org/pdf/2001.07488.pdf
Tarean 4y ago
The optics library is a bit stricter, using separate types with implicit conversions to give better type errors, and the subtyping diagram is here https://hackage.haskell.org/package/optics-0.4.2/docs/Optics.html#g:3 https://hackage.haskell.org/package/optics-0.4.2/docs/Optics... The lens documentation has this diagram https://i.imgur.com/ALlbPRa.png https://i.imgur.com/ALlbPRa.png These both skip over indexed versions, and some niche optics like grates aren't in the libraries yet afaik