%% Ownedby-relationship in monopoly
ownedby(bank,weststation).
%% Account-Value:
account(player1,1500).
%% Prices
price(weststation,200).
%% Buy an estate in monopoly
buy(X,Y):-
ownedby(bank,X),
!,
retract(ownedby(bank, X)),
assert(ownedby(Y,X)),
price(X,Price),
account(Y,Accountold),
retract(account(Y,Accountold)),
assert(account(Y,Accountold-Price)).
%% Example:
buy(player1,weststation).
%% RESULT:
account(player1,X).
1500-200
所以字符串1500和200连接在一起,但没有数字被减去...... :(什么是原因?
答案 0 :(得分:0)
您的规则需要更正
...
NewValue is Accountold-Price,
assert(account(Y,NewValue)).