Range expressions are used to index into arrays.
x[0..3]
references the first four elements of array x.
Limits: interpretation of negative ranges? Are we allowing negative indices?
Implicit ranges.
Explicit ranges. Q: does x<=y? If we allow negative indices then yes, because we need to be able to express empty ranges, when x>y.
Compile-time (meta-language) interpretation.
See chapter on compile-time flow-control (loops and conditionals).