利用归结原理对子句集中的子句进行归结代码

以下是利用归结原理对子句集中的子句进行归结的 Python 代码：

def unify_var(var, x, theta):
    if var in theta:
        return unify(theta[var], x, theta)
    elif x in theta:
        return unify(var, theta[x], theta)
    else:
        theta[var] = x
        return theta

def unify(x, y, theta):
    if theta is None:
        return None
    elif x == y:
        return theta
    elif isinstance(x, str) and x.islower():
        return unify_var(x, y, theta)
    elif isinstance(y, str) and y.islower():
        return unify_var(y, x, theta)
    elif isinstance(x, list) and isinstance(y, list) and len(x) == len(y):
        return unify(x[1:], y[1:], unify(x[0], y[0], theta))
    else:
        return None

def resolve(c1, c2):
    for l1 in c1:
        for l2 in c2:
            theta = unify(l1, ~l2, {})
            if theta is not None:
                resolvent = set(c1).union(set(c2))
                resolvent.remove(l1)
                resolvent.remove(l2)
                for key in theta:
                    resolvent.add(theta[key])
                return resolvent
    return None

def resolution(clauses):
    new_clauses = set(clauses)
    while True:
        n = len(new_clauses)
        pairs = [(new_clauses[i], new_clauses[j]) for i in range(n) for j in range(i+1,n)]
        for (c1, c2) in pairs:
            resolvent = resolve(c1, c2)
            if resolvent is not None:
                if not resolvent:
                    return True
                new_clauses.add(frozenset(resolvent))
        if len(new_clauses) == n:
            return False

其中，`unify_var` 函数用于统一变量，`unify` 函数用于统一两个项，`resolve` 函数用于根据两个子句进行归结，`resolution` 函数则是主函数，用于对整个子句集进行归结。其中，`clauses` 是一个包含所有子句的列表，每个子句又是一个包含文字的集合。如果归结成功，则返回 `True`，否则返回 `False`。