def trans_infix_suffix(line):
st = SStack()
exp = []
for x in token(line):
if x not in infix_operators:
exp.append(x)
elif st.is_empty() or x == '(':
st.push(x)
elif x == ')':
while not st.is_empty() and st.top() != '(':
st.append(st.pop())
if st.is_empty():
raise ValueError
st.pop()
else:
while (not st.is_empty() and property[st.top()] >= property[x]
): # 当top是*/，x是+-的时候，将top加入
exp.append(st.pop())
st.push(x)
while not st.is_empty():
if st.top() == '(':
raise ValueError
exp.append(st.pop())
return exp
def postorder_nonrec(t, proc):
s = SStack()
while t is not None or not s.is_empty():
while t is not None: # 下行，直到找到栈顶的两子数为空
s.push(t)
t = t.left if t.left is not None else t.ringt # 这里不用 try，如果t下面没有子树不会报错，而是None
# 看结点定义def __init__(self,dat,right=None,left=None)
t = s.pop()
proc(t.data)
if not s.is_empty() and s.top.left == t: # 如果t是现在栈顶的左子树
t = s.top().right
else:
t = None #