例如: if (T->f == '~' && T->lchild != NULL)
T->b = !(T->lchild->b);
else if (T->f == '~' && T->rchild != NULL)
T->b = !(T->rchild->b);
else if (T->f == '&')
T->b = T->lchild->b & T->rchild->b;
else if (T->f == '|')
T->b = T->lchild->b | T->rchild->b;
是字符串哦,T->f == “&”,是说t结构体的元素f是否是这个符号哦
&&是且
||是或
先执行逻辑运算,然后把运算结果赋值给等号前面的变量