python 示例分享---逻辑推理编程解决八皇后
可以和Haskell，Prolog一样做到模式匹配，
建立逻辑推到规则，描述问题，得出答案。
frompyDatalogimportpyDatalog
pyDatalog.create_atoms('N,N1,X,Y,X0,X1,X2,X3,X4,X5,X6,X7')
pyDatalog.create_atoms('ok,queens,next_queen,pred,pred2')
size=8
ok(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)))