On 2020-03-31 20:48 +0700, Duy Nguyen wrote:
>>What do you mean by "passing error messages around" in everyday
>>programming? Usually, one would invoke the current error handler
>>or a special failure continuation to signal errors and wouldn't
>>treat errors through a data-directed programming style.
>>
>
>Ah that's what I missed. But I think we're dealing with data-directed
>programming style here though (returning #f as fail), perhaps not
>severe enough to change control flow, just log the errors for more
>analysis later.

An example that comes to mind is the (original) Parsec[1] parser’s
approach of building up either (A) a collection of parses or (B) a
collection of all the errors encountered in parsing.  This is a
natural use for Either, I think; you can have, say, a function which
constructs a list of values or a list of error-reports, and know
precisely which is which.

[1]: Meijer & Leijen, "Parsec: A Practical Parsing Library"

--
Wolfgang Corcoran-Mathe  <xxxxxx@sigwinch.xyz>

"It from bit." --John Wheeler