From: Joachim Schimpf <js10_at_icparc.ic.ac.uk>

Date: Mon 29 Mar 1999 04:34:12 PM GMT

Message-ID: <36FFAB84.6201DD56@icparc.ic.ac.uk>

Date: Mon 29 Mar 1999 04:34:12 PM GMT

Message-ID: <36FFAB84.6201DD56@icparc.ic.ac.uk>

Tallys Hoover Yunes wrote: > > Hello, > > I'd like to use a modified version of the constraint > atmost, where, instead of having "at most k elements of > a list equal to a certain number", I would have "at most > k elements of a list greater than a certain number". > > Has anyone seen/implemented such a constraint ? > Perhaps, starting with the code of the atmost constraint > it would be easy to implement this new constraint. > > By the way, is there an easy way to implement an > "atleast" constraint ? > > Best regards, > Tallys Yunes Here is the code for the occurrences/3 constraint (from the fd_global library). It should not be too difficult to modify it for your purposes. % % occurrences(++Value, +List, ?N) % The value Value occurs in List N times. % Operationally: N gets updated to reflect the number of % possible occurrences in the List. List elements may get % instantiated to Value, or Value may be removed from their % domain if required by N. % :- lib(fd). occurrences(Value, List, N) :- var(Value), suspend(occurrences(Value, List, N), 3, Value->inst). occurrences(Value, List, N) :- nonvar(Value), occurrences(Value, List, N, 0). occurrences(Value, List, N, Occ) :- count_vars(Value, List, Occ, Lower, Occ, Upper, VarsWithValue), % use call_priority to make updates and re-suspend atomic call_priority(occurrences1(Value, VarsWithValue, N, Lower, Upper), 2). occurrences1(Value, VarsWithValue, N, Lower, Upper) :- Lower #<= N, N #<= Upper, ( N == Lower -> ( foreach(X, VarsWithValue), param(Value) do dvar_remove_element(X, Value) ) ; N == Upper -> ( foreach(X, VarsWithValue), param(Value) do X = Value ) ; suspend(occurrences(Value, VarsWithValue, N, Lower), 4, [VarsWithValue->any, N->min, N->max]) ). % count_vars(+Value,+Vars,-Lower,-Upper,-VarsWithValue) % Given an integer value and a list of finite domain variables % Returns a lower and an upper bound of the times this value % appear in the variable list as well as the variables which % may or may not hold this value in the future. % The lower bound refers to the number of times a variable was % instantiated to the value. % The upper bound refers to the number of uninstantiated variables % which can still take this value. % The VarsWithValue are the uninstantiated variables... count_vars(_,[],Lower,Lower,Upper,Upper,[]). count_vars(Value,[H|T],Lower1,Lower,Upper1,Upper,VarsWithValue) :- dvar_domain(H,DH), ( dom_check_in(Value,DH) -> Upper2 is Upper1 + 1, % Value in domain ( H == Value -> Lower2 is Lower1 + 1, % H is instantiated to Value! VarsWithValue = MoreWithValue ; Lower2 = Lower1, VarsWithValue = [H|MoreWithValue] ), count_vars(Value,T,Lower2,Lower,Upper2,Upper,MoreWithValue) ; count_vars(Value,T,Lower1,Lower,Upper1,Upper,VarsWithValue) ). ------------------------------------------------------------------------ Joachim Schimpf / phone: +44 171 594 8187 IC-Parc, Imperial College / mailto:J.Schimpf@ic.ac.uk London SW7 2AZ, UK / http://www.icparc.ic.ac.uk/eclipseReceived on Tue Mar 30 10:52:03 1999

*
This archive was generated by hypermail 2.1.8
: Wed 16 Nov 2005 06:07:04 PM GMT GMT
*