[mercury-users] Impurity annotations on modes?

[Ralph Becket]

Peter Hawkins, Thursday, 30 June 2005:
> Hi...
> 
> Is it possible for some modes of a predicate to be impure, but not others?
> In particular I would like to write this code:
> 
> :- func ask_var_value(constraint_variable) = value_type.
> :- impure mode ask_var_value(ia) = (out) is det.
> :- mode ask_var_value(in) = (out) is det.
> 
> (In other words, it's only impure to ask the value of a variable if it 
> isn't known to be ground)
> 
> Doable?

Not at the mo.  Anyone interested in doing a Ph.D. on mode polymorphism
(which is something that *really* needs research) should apply within!
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