[Haskell-cafe] ANNOUNCE: AbortT-transformers version 1.0

Henning Thielemann schlepptop at henning-thielemann.de
Thu Sep 9 12:16:05 EDT 2010

Colin Paul Adams schrieb:
>>>>>> "Henning" == Henning Thielemann <lemming at henning-thielemann.de> writes:
>     Henning> On Wed, 8 Sep 2010, Gregory Crosswhite wrote:
>> ExceptionT is a different matter because it handles "fail" as an
>     >> uncaught error and places no restrictions on the error type, so
>     >> one could implement the same functionality as AbortT by using
>     >> ExceptionalT and requiring the end result be a monadic value of
>     >> type "ExceptionalT e m e", where the exception and result types
>     >> are the same.  However, I believe that it is better to have the
>     >> AbortT functionality available as a separate simple library
>     >> specialized for this purpose than to have its functionality
>     >> buried inside a more general library that is really intended to
>     >> be used for a different purpose.
>     Henning> If we get rid of the notion of an exception as being
>     Henning> something bad, and instead consider an exception as being
>     Henning> early exit for whatever reason, I see no problem. E.g. you
>     Henning> may well use an exception to terminate a successful search,
>     Henning> returning the search result as exception value.
> So where is the exceptional nature? Is a successful conclusion to a
> search so exceptional?

You search as long as you don't find what you are looking for. So not
finding what you search seems to be the rule and finding it seems to be
the exception. :-)

> It seems to me that you want to get rid of the notion of an exception as
> something exceptional, in which case it would be better to give it a
> different name.

English is not my native tongue. If 'abort' is more appropriate than
'exception' we may rename modules from Exception to Abort.

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