Allow expressions for slice values

[innovate-invent]

With let() and unquoted literals we can have dynamic slice expressions.

Replace

slice-expression  = [number] ":" [number] [ ":" [number] ]

with

slice-expression  = [expression / number ] ":" [expression / number ] [ ":" [expression / number ] ]

[springcomp]

Can you elaborate on one scenario where this would be useful?

I think you suggest using expressions that consist in using the let() function inside slice-expressions. However, the let() function does not have a defined return value so I fail to see how this would behave?

[innovate-invent]

A trivial example would be cropping two arrays to the same length:

search({short: [ a, b, c ], long: [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]}, long[:length( short )] )