Triple.Extra

[gampleman]

This adds a library for dealing with Triples (fixes #21).

I think the most controversial idea here are the swizzles. I'm happy to delete them for now if the other maintainers have qualms.

[lue-bird]

I can't say much because I've never used triples

• would be nice to still add the codegen code in a separate folder in case one wants to change the documentation in the future for example
• the swizzles do in fact seem only very rarely useful and I'd always prefer explicit construction personally
• fromListHead: maybe rename it to fromListBeginning or fromBeginningOfList?
• joinBy seems somewhat inconsistent because
  • we don't have sumBy, productBy etc either
  • in all other -By operations like minimumBy or sortBy the given function(s) do not map the result which means a name like joinMap is probably more consistent
  • I feel like the arguments in the explicit join sep (map a b c triple) are much more clear

[miniBill]

triple, first, second, third are obviously good

The swizzles I'd avoid having in core-extra

The other functions feel... weird? Like, is doing the product of three numbers in a triple a common operation at all? Or sorting them?

[gampleman]

Hm I tend to agree with some of these sentiments. The functions I added are just stuff we have in Tuple.Extra. But perhaps it's better to be more conservative to begin with.

I'll probably like to keep the sorting functions (or at least sortWith) since they're somewhat challenging to implement correctly.

[lydell]

I’m curious about the swizzles. Is that something you came up with yourself, or something you’ve seen somewhere else? Also just for curiosity, what could they be used for?

[gampleman]

I’m curious about the swizzles. Is that something you came up with yourself, or something you’ve seen somewhere else? Also just for curiosity, what could they be used for?

They're a common feature of GPU oriented languages like GLSL. I always found them super fun, but perhaps the reason they'd be useful in those contexts is that those languages generally compute around fix length vectors, whereas actually triples are fairly rare in Elm (and we don't actually particularly want to promote them).

So you can do things like:

vec4 opaque = vec4(color.rgb, 1.0);

vec3 mirrored = position.yxz;

vec3 onlyRed = color.rrr;

and so on