<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-2" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> <big>Dear experienced ones, in aim to provide a handy "one arg per config" interface to Tk configuration for the mercury_tk interface, I have a question: First, here is some surrounding code: :-type data ---> forename(string); surname(string); ... :-inst forenameG ---> forename(ground). :-inst surnameG ---> surname(ground). :-inst forenameF ---> forename(free). :-inst surnameF ---> surname(free). :-pred isForename(<a class="moz-txt-link-freetext" href="data::(forenameF">data::(forenameF</a> >> forenameG), io::di, io::uo) is det. isForename(forename("F"), !IO). :-pred isSurname(<a class="moz-txt-link-freetext" href="data::(surnameF">data::(surnameF</a> >> surnameG), io::di, io::uo) is det. isSurname(surname("S"), !IO). The attached code sample runs fine as long as there is only a single mode, :-pred isName(data, io, io). :-mode isName((forenameF >> forenameG), di, uo) is det. isName(F::(forenameF >> forenameG), I::di, O::uo) :- isForename(F, I, O). i.e. there are no compiler complaints. But once I use more modes, :-pred isName(data, io, io). :-mode isName((forenameF >> forenameG), di, uo) is det. :-mode isName((surnameF >> surnameG), di, uo) is det. :-pragma promise_pure( isName/3). isName(S::(surnameF >> surnameG), I::di, O::uo) :- isSurname(S, I, O). isName(F::(forenameF >> forenameG), I::di, O::uo) :- isForename(F, I, O). I reveive the following error message: configMode.m:029: In clause for `isName(((configMode.forenameF) >> configMode.m:029: (configMode.forenameG)), di, uo)': configMode.m:029: in argument 1 of call to predicate configMode.m:029: `configMode.isForename/3': configMode.m:029: mode error: variable `F' has instantiatedness `free', configMode.m:029: expected instantiatedness was configMode.m:029: `bound(configMode.forename(free))'. configMode.m:026: In clause for `isName(((configMode.surnameF) >> configMode.m:026: (configMode.surnameG)), di, uo)': configMode.m:026: in argument 1 of call to predicate configMode.m:026: `configMode.isSurname/3': configMode.m:026: mode error: variable `S' has instantiatedness `free', configMode.m:026: expected instantiatedness was configMode.m:026: `bound(configMode.surname(free))'. Is there anybody to explain me this message and - even better ;-) - tell me a way to get this problem solved? This would mean I could begin finishing mercury_tk, as such an interface to Tk configurations, configName(free) >> configName(ground), would appear quite satisfying to me. Thank you in advance, Nick </big> </body> </html>