Add more glossary terms

[athas]

I have begun work on a glossary of terms that might be useful to new Futhark programmers. I'll leave this issue open for a little while as invitation to suggest other terms that we might want to add.

[zfnmxt]

• size coercions; they're also called shape coercions in some places. (Maybe they should be consistently named a single thing.)

• (ir)regular

• backend

• attribute

• higher-order (type | function)

• (size | type) annotation

[Munksgaard]

Great initiative!

Ideas off the top of my head: lifted types (^), coalescing, irregular vs regular parallelism

[athas]

size coercions; they're also called shape coercions in some places. (Maybe they should be consistently named a single thing.)

Which name do you think is best?

[athas]

I can argue "size coercion" is better, since you can only change sizes of shapes, not ranks. Hence, "shapes" don't change, only sizes do.

[zfnmxt]

I can argue "size coercion" is better, since you can only change sizes of shapes, not ranks. Hence, "shapes" don't change, only sizes do.

I agree.

[athas]

Thanks! I included most of your suggestions. Exclusions:

• higher-order (type | function): if you don't know what a higher-order function is, then the Futhark glossary is the wrong thing to read. And what is a higher-order type?
• (size | type) annotation: I kind of want to get away from this nomenclature, but maybe I'll change my mind. (They are not annotations, they are ascriptions, and they are all ultimately type ascriptions.)
• coalescing: You mean GPU memory transaction implementation details? What could we say about this that would be useful? The compiler will never scream this word at you.

[zfnmxt]

And what is a higher-order type?

You tell me! https://github.com/diku-dk/futhark/blob/4d53cb450d7cb4fa4308d72f256c1a7f068a7d89/src/Language/Futhark/TypeChecker/Unify.hs#L929