[m-users.] "this is not allowed in a type constructor's argument"

[Volker Wysk]

Hi!

When I do this:

:- func actions = assoc_list(string, 
                             (pred(string::in, string::out) is det)).

I get this:

test2.m:009: In `:- func' declaration:
test2.m:009:   in the return value
test2.m:009:   error: the type `(pred((string :: in), (string :: out)) is
det)'
test2.m:009:   contains higher order inst information, but this is not
allowed
test2.m:009:   in a type constructor's argument.

Why doesn't this work? How should it be done ...?

Bye, Volker
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