[m-users.] Converting an exception to a different exception

[Volker Wysk]

P.S.:

I'm aware of the map.search function/predicate. It just occured to me that
it was interesting. In Haskell, there's a function (forgot its name), that
can do exactly that.


Am Donnerstag, den 20.05.2021, 07:39 +0200 schrieb Volker Wysk:
> Hi
> 
> I want do convert an exception from one type to another. Like this:
> 
> 
> :- pred dir_to_name(pages::in, string::in, string::out) is det. 
> 
> dir_to_name({ _, DirNameM }, Dir, Name) :-
>     ( try []                                                     
>           map.lookup(DirNameM, Dir, Name)
>       then  
>           true
>       catch software_error(_) ->
>           throw("Unknown page directory " ++ quote(Dir))
>     ).
> 
> 
> This won't compile, because "A try goal has determinism cc_multi." (Mercury
> Reference Manual, chapter 12).
> 
> Is there any way to do this?
> 
> Regards,
> Volker
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