Array indexing and slice syntax

[LightAndLight]

Indexing

I currently use array.get to access array elements. It's partial, and I've suggested total and partial versions in #386 (get and get!).

I might want array indexing syntax that desugars to get!. I like using . for projection, so I was thinking something like x.1, x.(1), or x.[1].

Array indexing in other languages often uses brackets (x[1]), and arrays already use brackets ([1, 2, 3]), so of the three options above I prefer x.[1].

Slicing

Once we have an indexing syntax, I'd like slice syntax. Something like x.[a..b] or x.[a:b]. I prefer offset/length slicing rather than start/end(inclusive/exclusive) slicing. So I favour x.[a:b] over x.[a..b]; to me .. seems to lend itself better to the start/end style. The only problem with x.[a:b] is that : already means "has type", and I'd prefer to keep it that way. Perhaps ; instead? How does that fit with #210? What about a plain ,?

:

• x.[1:2] - create a sub-array of length 2 starting from index 1
• x.[3:] - create a sub-array of length array.length x - 3 (include all remaining elements) starting from index 3

;

• x.[1; 2]
• x.[3;]

Kinda icky

,

• x.[1, 2]
• x.[3,]

Yeah, no.

Other languages

Wikipedia article: https://en.wikipedia.org/wiki/Array_slicing

Language comparison: https://en.wikipedia.org/wiki/Comparison_of_programming_languages_(array)#Slicing