[m-users.] Insts of tuple types?

[Volker Wysk]

Hello.

I have an argument of this type:

    maybe(
        { (pred(io, io)),
          place_data
        }
    )

I need to specify a higher order inst because the first component is a
predicate. What is the inst? This inst doesn't work:

    :: out(
        maybe(
            { pred(di, io) is det,
              ground
            }
        ))

I get this error message:

amend.m:099: In declaration of predicate `amend_new_file_place'/5:
amend.m:099:   error: undefined inst `{}'/2.


Cheers,
Volker
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