It's fairly correct and up-to-date although I note that the constraint example 'send more money' given is stated as 'Prolog' when it really uses ECLiPSe Prolog constraint syntax (alldifferent/1, labelling/1 and '#' integer constraints): If you're really interested in constraint based languages then have a look at ECLiPSe (yes shameless plug and I'm biased ;-): http://www.eclipse-clp.org and in particular the language tutorial: http://www.eclipse-clp.org/doc/tutorial/index.html ECLiPSe is robust and mature enough for industrial application development, most notably by Cisco and CrossCore Optimization. Incidentally, we've often seen a lot of traffic on here about Sudoku solvers and I've always wanted to post the ECLiPSe solution (neat when you consider the length of the sudoku/2 predicate ;-) : % ECLiPSe sample code - Sudoku problem % % This is a puzzle, originating from Japan, where you have a % 9x9 grid, consisting of 9 3x3 sub-grids. The challenge is % to fill the grid with numbers from 1 to 9 such that every row, % every column, and every 3x3 sub-grid contains the digits 1 to 9. % Some of these numbers are given, which is the way different % instances of the problem are made. The solution is usually unique. % % Compile this file with ECLiPSe and call e.g. % :- solve(1). % % Author: Joachim Schimpf, IC-Parc % :- lib(ic). :- import alldifferent/1 from ic_global. solve(ProblemName) :- problem(ProblemName, Board), print_board(Board), sudoku(3, Board), print_board(Board). sudoku(N, Board) :- N2 is N*N, dim(Board, [N2,N2]), Board[1..N2,1..N2] :: 1..N2, ( for(I,1,N2), param(Board,N2) do Row is Board[I,1..N2], alldifferent(Row), Col is Board[1..N2,I], alldifferent(Col) ), ( multifor([I,J],1,N2,N), param(Board,N) do ( multifor([K,L],0,N-1), param(Board,I,J), foreach(X,SubSquare) do X is Board[I+K,J+L] ), alldifferent(SubSquare) ), term_variables(Board, Vars), labeling(Vars). print_board(Board) :- dim(Board, [N,N]), ( for(I,1,N), param(Board,N) do ( for(J,1,N), param(Board,I) do X is Board[I,J], ( var(X) -> write(" _") ; printf(" %2d", [X]) ) ), nl ), nl. %---------------------------------------------------------------------- % Sample data %---------------------------------------------------------------------- problem(1, []( [](_, _, 2, _, _, 5, _, 7, 9), [](1, _, 5, _, _, 3, _, _, _), [](_, _, _, _, _, _, 6, _, _), [](_, 1, _, 4, _, _, 9, _, _), [](_, 9, _, _, _, _, _, 8, _), [](_, _, 4, _, _, 9, _, 1, _), [](_, _, 9, _, _, _, _, _, _), [](_, _, _, 1, _, _, 3, _, 6), [](6, 8, _, 3, _, _, 4, _, _))). Cheers Andy Peter Verswyvelen wrote:
Jerzy Karczmarczuk wrote
Perhaps somebody can say more about constraint languages which replaced
Yes please! Of example, how correct is http://en.wikipedia.org/wiki/Constraint_programming?
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* Andrew Cheadle email: a.cheadle@doc.ic.ac.uk * * Department of Computing http://www.doc.ic.ac.uk/~amc4/ * * Imperial College London * *********************************************************************