void
gen_aux (const Grammar &g, const std::string &start, std::vector<std::string> &result)
{
TokenStack lifo;
expand_aux (g, start, lifo);
while (!lifo.empty())
{
const std::string curr_word = lifo.top();
lifo.pop();
if (!bracketed (curr_word))
{
result.push_back (curr_word);
}
else
{
expand_aux (g, curr_word, lifo);
}
}
}
// 逆波兰式计算求值
bool CalcExpr(const TokenVector & input, const TokenVector & expr, Token & result)
{
TokenStack stack;
TokenVector::const_iterator it = expr.begin();
for (; it != expr.end(); ++it)
{
if (it->type == INT || it->type == FLOAT || it->type == BOOL)
{
stack.push(*it);
}
else if (it->type == ARG)
{
if (it->value.index >= input.size()) return false;
const Token & a = input[it->value.index];
if (a.type == INT || a.type == FLOAT || a.type == BOOL)
{
stack.push(a);
}
else
{
return false;
}
}
else if (it->type == RAND)
{
Token a;
a.type = INT;
a.value.i = rand();
stack.push(a);
}
else if (it->type == OP)
{
if (stack.size() < 2) return false;
Token a = stack.top();
stack.pop();
Token b = stack.top();
stack.pop();
Token c;
if (GetValue(it->value.op, b, a, c))
{
stack.push(c);
}
else
{
return false;
}
}
}
if (!stack.empty())
{
result = stack.top();
return true;
}
else
{
return false;
}
}
// 把解析好的表达式转换成逆波兰式
bool ConvertExpr(const TokenVector & input, TokenVector & output)
{
TokenStack stack;
output.clear();
TokenVector::const_iterator it = input.begin();
for (; it != input.end(); ++it)
{
if (it->type == OP)
{
// 左括号，直接压进操作符栈
if (it->value.op == LEFT)
{
stack.push(*it);
}
// 右括号，从栈里弹出操作符，直到碰到右括号
else if (it->value.op == RIGHT)
{
bool find_left = false;
while (!stack.empty())
{
if (stack.top().value.op == LEFT)
{
find_left = true;
stack.pop();
break;
}
else
{
output.push_back(stack.top());
stack.pop();
}
}
if (!find_left) return false;
}
// 其它操作符，和栈顶操作符比较优先级
else
{
while (!stack.empty() && stack.top().value.op != LEFT &&
OPPriority(stack.top().value.op) >= OPPriority(it->value.op))
{
output.push_back(stack.top());
stack.pop();
}
stack.push(*it);
}
}
// 非操作符直接输出
else
{
output.push_back(*it);
}
}
while (!stack.empty())
{
output.push_back(stack.top());
stack.pop();
}
return true;
}
