Is it possible to implement `[]` as an iterator? Right now I have `proc []`
operator implementation for slice that builds `seq[T]` (allocation), but I
often use it as `for sub in node[1..n]`, so there is no real use to build an
intermediate sequence. I tried
type Custom = distinct string
iterator `[]`(a: Custom, r: HSlice[int, int]): char =
for q in r:
yield a.string[q]
for val in Custom("test")[2..3]:
echo val
Run
but it fails with compilation error
Error: type mismatch: got <prog.Custom, HSlice[system.int, system.int]>
but expected one of:
iterator `[]`(a: Custom; r: HSlice[int, int]): char
first type mismatch at position: 0
proc `[]`(s: string; i: BackwardsIndex): char
first type mismatch at position: 0
Run
First overload seems to fit perfectly (`a: Custom; r: HSlice[int, int]`), but
compilation still fails. If I use `[]` explicitly (`[](1, 2 .. 3)`) it works,
but that looks quite bad.
It is possible to use regular operators as iterators - `system.nim` defines
`iterator ..` (<https://nim-lang.org/docs/system.html#...i%2CT%2CT>)
