Python example sharing --- logic reasoning programming solution to eight queens

The eight queens issue is an ancient and famous issue and is a typical case of backtracking algorithms. This problem was raised by Max & #183, an international chess player, who proposed in 1848 that eight queens should be placed on 8x8 chess so that they could not attack each other, that is to say, neither of the two queens can be in the same row, column, or diagonal line. It can match the pattern like Haskell and Prolog,

Create logic to push to rules, describe the question, and get the answer.

from pyDatalog import pyDatalogpyDatalog.create_atoms( 'N, N1, X, Y, X0, X1, X2, X3, X4, X5, X6, X7' )pyDatalog.create_atoms( 'ok, queens, next_queen, pred, pred2' )size = 8ok( X1, N, X2 ) <= ( X1 != X2 ) & ( X1 != X2 + N ) & ( X1 != X2 - N )pred( N, N1 )  <= ( N > 1 ) & ( N1 == N - 1 )queens( 1, X ) <= ( X1._in( range( size ) ) ) & ( X1 == X[0] )queens( N, X ) <= pred( N, N1 ) & queens( N1, X[:-1] ) & next_queen( N, X )pred2( N, N1 )   <= ( N > 2 ) & ( N1 == N - 1 )next_queen( 2, X ) <= ( X1._in( range( 8 ) ) ) & ok( X[0], 1, X1 ) & ( X1 == X[1] )next_queen( N, X ) <= pred2( N, N1 ) & next_queen( N1, X[1:] ) & ok( X[0], N1, X[-1] ) print( queens( size, ( X0, X1, X2, X3, X4, X5, X6, X7 ) ) )