binary sudoku in swi prolog

Question

As a prolog newbie, I wanted to try to implement a binary sudoku solver.(Code is below, swi-prolog). Binary sudoku is explained here : https://cstheory.stackexchange.com/questions/16982/how-hard-is-binary-sudoku-puzzle However, when performing the following query : ``` binarySudoku([[1,0],[0,1]]). I get "true." binarySudoku([[1,_],[_,_]]). I get "false." ``` Now obviously it shouldn't return false as there is a solution... Why is this happening/how can I fix this? ``` :-use_module(library(clpfd)). validRow(Row) :- Row ins 0..1, length(Row,L), sum(Row,#=,L/2). matrixNth(Matr,X,Y,El) :- nth1(Y,Matr,CurRow), nth1(X,CurRow,El). allDifferent([]). allDifferent([X|Y]) :- not(member(X,Y)), allDifferent(Y). invalid(Rows,X,Y) :- AboveY is Y-1, BelowY is Y+1, matrixNth(Rows,X,Y,1), matrixNth(Rows,X,AboveY,1), matrixNth(Rows,X,BelowY,1). invalid(Rows,X,Y) :- LeftX is X-1, RightX is X+1, matrixNth(Rows,X,Y,1), matrixNth(Rows,LeftX,Y,1), matrixNth(Rows,RightX,Y,1). binarySudoku(Rows) :- length(Rows…

Accepted Answer

Instead of `(\+)/1`, which is not logically sound in this case, use the pure constraint `dif/2`: Your code works as expected of you change the line `not(member(X,Y))` to:

`maplist(dif(X), Y)`

Example query (notice that I also use a_more_readable_naming_convention insteadOfMixingTheCases):

```
?- binary_sudoku([[1,A],[B,C]]), label([A,B,C]).
A = B, B = 0,
C = 1 ;
false.
```

+1 for using CLP(FD), which is a good fit for this task.

binary sudoku in swi prolog

Solution

Problem