Wrong documentation for String.mapi

[phasetr]

This is not a bug in code, but for documentation, I think, but I'd like to confirm intention.

The sample code for String.mapi is input |> String.mapi (fun i c -> (i, c)), but this lambda produces int * char, so we have an error when we run this sample. I somehow correct the document, e.g, input |> String.mapi (fun _ c -> c), but what is a better example for String.mapi? Or is the intent of String.mapi (and/or String.map?) originally to be Seq.map, e.g., mapping should be int -> 'char -> 'U?