[m-dev.] generic result types

[Julien Fischer]

On Wed, 18 Feb 2009, Peter Ross wrote:

> Hi,
>
> Do people think it would be useful to add the following generic types
> to the standard library?
>
> :- type result(T, E)
>    --->    ok(T)
>    ;       error(E)
>    .
>
> :- type partial_result(T, E) == partial_result(T, T, E).
>
> :- type partial_result(T, P, E)
>    --->    ok(T)
>    ;       error(P, E)
>
> :- type result(E)
>    --->    ok
>    ;       error(E)
>    .

result/2 and result/1 almost already exist in the form of the
maybe_error/[01] types.  Making them polymoprhic in the error type would
give you the above.  Maybe, maybe_partial_result/3 could be added to the 
maybe module?

Julien.
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