python - 类型错误 : Can't convert 'node' object to str implicitly

Question

对于下面的代码——

Reg_Stack = ['R5', 'R4', 'R3', 'R2', 'R1', 'R0']
Temp_Stack = ['T5', 'T4', 'T3', 'T2', 'T1', 'T0']
operator_precedence = {'(' : 0, ')' : 0, '+' : 1, '-' : 1, '*' : 2, '/' : 2}

def gen_code(n):
    if(n.left == None and n.right == None):
        print("MOV " + n.value + "," + Reg_Stack[-1])
    else:
        if(n.right.label == 0):
            gen_code(n.left)
            print(operator(n.value) + " " + n.right.value + "," + Reg_Stack[-1])

        elif((n.left.label < n.right.label) and (n.left.label < len(Reg_Stack))):
            swap()
            gen_code(n.left)
            R = Reg_Stack.pop()
            gen_code(n.left)
            print(operator(n.value) + " " + n.left.value + "," + Reg_Stack[-1])
            Reg_Stack.append(R)
            swap()

        elif((n.right.label < n.left.label) and (n.right.label < len(Reg_Stack))):
            gen_code(n.left)
            R = Reg_Stack.pop()
            gen_code(n.right)
            print(operator(n.value) + " " + n.right.value + "," + Reg_Stack[-1])
            Reg_Stack.append(R)

        else:
            gen_code(n.right)
            T = Temp_Stack.pop()
            print("MOV " + Reg_Stack[-1] + "," + T)
            gen_code(n.left)
            Temp_Stack.append(T)
            print(operator(n.value) + " " + T + "," + Reg_Stack[-1])

def operator(v):
    if(v == "+"):
        return "ADD"
    if(v == "-"):
        return "SUB"
    if(v == "*"):
        return "MUL"

def swap():
    a1 = Reg_Stack.pop()
    b1 = Temp_Stack.pop()
    Reg_Stack.append(b)
    Temp_Stack.append(a)

class node(object):
    def __init__(self, value='', lvalue=0, node1 = None, node2 = None):
        self.value = value
        self.left = node1
        self.right = node2
        self.label = lvalue


a = node('a', 1)
b = node('b', 1)
c = node('c', 1)
d = node('d', 0)

q1 = node('*', 1, c, d)
q2 = node('-', 2, b, q1)
root = node('+', 0, a, q2)
gen_code(root)

我遇到了错误-

C:\Python33>python main.py
Traceback (most recent call last):
  File "main.py", line 67, in <module>
    gen_code(root)
  File "main.py", line 15, in gen_code
    gen_code(n.left)
  File "main.py", line 7, in gen_code
    print("MOV " + n.value + "," + Reg_Stack[-1])
TypeError: Can't convert 'node' object to str implicitly

gen_code() 函数的输入是一棵带标签的树。我尝试过不同的树并且代码有效。但只有在这种情况下，我才会收到上述错误。我做错了什么？

Answer 1

这个问题主要是因为你的 swap() 函数 -

def swap():
    a1 = Reg_Stack.pop()
    b1 = Temp_Stack.pop()
    Reg_Stack.append(b)
    Temp_Stack.append(a)

您正在从 Reg_Stack 和 Temp_Stack 中删除 strings，然后将 node 附加到它。所以当你这样做之后 -

Reg_Stack[-1]

您从 swap() 函数中取回您附加的 node 对象。这会导致您在尝试将其添加(连接)到 str 时看到的错误。

您应该添加节点的值，而不是节点本身。示例-

def swap():
    a1 = Reg_Stack.pop()
    b1 = Temp_Stack.pop()
    Reg_Stack.append(b.value)
    Temp_Stack.append(a.value)

在这个改变之后我得到的结果是 -

MOV a,b
MOV a,R1
ADD a,R1

但不确定其他逻辑是否正确。