Modelling

8.3 Modelling

The problem modelling code must:

Create the variables with their initial domains
Setup the constraints between the variables

A simple example is the “crypt-arithmetic” puzzle, SEND+MORE = MONEY. The idea is to associate a digit (0-9) with each letter so that the equation is true. The ECLⁱPS^e code is as follows:

:- lib(ic).

sendmore(Digits) :-
    Digits = [S,E,N,D,M,O,R,Y],

% Assign a finite domain with each letter - S, E, N, D, M, O, R, Y - 
% in the list Digits
    Digits :: [0..9],

% Constraints
    alldifferent(Digits),
    S #\= 0,
    M #\= 0,
                 1000*S + 100*E + 10*N + D
               + 1000*M + 100*O + 10*R + E
    #= 10000*M + 1000*O + 100*N + 10*E + Y,

% Search
    labeling(Digits).