[R6RS] Protocol for handling encoding/decoding errors

[William D Clinger]

Mike wrote:
> Here's a first cut at it, mainly for Will:
> 
> For encoding errors...

I think your first cut is good enough for the 1 Sept
draft.

> This has the disadvantage that a handler may want to try handling the
> error, decline and leave the handling to some higher-level handler,
> but that "try handling" involves removing data from the port, which is
> not reversible.  I don't know an easy way around this.

It may not be "easy", but your first cut plus the rest
of R6RS does provide a way: combine the condition with
another that contains the bytes that were read during
the first attempt to handle the error.  A higher-level
handler that understands the combined condition would
then be able to recover.

Our responsibility is to provide the mechanisms, not
(all of) the solutions.

Will