Created
October 17, 2022 09:03
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Basic calculator via Python 3
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class Cursor(): | |
def __init__(self, s): | |
self.s = ''.join(s.split()) | |
def is_remains(self, i=0): | |
return i < len(self.s) | |
def advance(self, n): | |
self.s = self.s[n:] | |
class Node(): | |
def __init__(self, c): | |
self.inner = PlusMinusNode(c) | |
def calc(self): | |
return self.inner.calc() | |
class PlusMinusNode(): | |
def __init__(self, c): | |
if not c.is_remains(): | |
raise | |
self.lhs = MulDivModNode(c) | |
self.rhs = [] | |
while c.is_remains(): | |
op = c.s[0] | |
if op == '+': | |
c.advance(1) | |
self.rhs.append([op, MulDivModNode(c)]) | |
elif op == '-': | |
c.advance(1) | |
self.rhs.append([op, MulDivModNode(c)]) | |
else: | |
break | |
def calc(self): | |
value = self.lhs.calc() | |
for rhs in self.rhs: | |
if rhs[0] == '+': | |
value += rhs[1].calc() | |
elif rhs[0] == '-': | |
value -= rhs[1].calc() | |
return value | |
class MulDivModNode(): | |
def __init__(self, c): | |
if not c.is_remains(): | |
raise | |
self.lhs = PowNode(c) | |
self.rhs = [] | |
while c.is_remains(): | |
op = c.s[0] | |
if op == '*': | |
c.advance(1) | |
self.rhs.append([op, PowNode(c)]) | |
elif op == '/': | |
c.advance(1) | |
self.rhs.append([op, PowNode(c)]) | |
elif op == '%': | |
c.advance(1) | |
self.rhs.append([op, PowNode(c)]) | |
else: | |
break | |
def calc(self): | |
value = self.lhs.calc() | |
for rhs in self.rhs: | |
if rhs[0] == '*': | |
value *= rhs[1].calc() | |
elif rhs[0] == '/': | |
print(rhs[0]) | |
value /= rhs[1].calc() | |
elif rhs[0] == '%': | |
value %= rhs[1].calc() | |
return value | |
class PowNode(): | |
def __init__(self, c): | |
if not c.is_remains(): | |
raise | |
self.lhs = LeafNode(c) | |
self.rhs = [] | |
while c.is_remains(): | |
op = c.s[0] | |
if op == '^': | |
c.advance(1) | |
self.rhs.append([op, LeafNode(c)]) | |
else: | |
break | |
def calc(self): | |
value = self.lhs.calc() | |
for rhs in self.rhs: | |
if rhs[0] == '^': | |
value **= rhs[1].calc() | |
return value | |
class LeafNode(): | |
def __init__(self, c): | |
if not c.is_remains(): | |
raise | |
if c.s[0] == '(': | |
c.advance(1) | |
self.node = Node(c) | |
if not c.is_remains() or c.s[0] != ')': | |
raise | |
c.advance(1) | |
else: | |
self.node = NumberNode(c) | |
def calc(self): | |
return self.node.calc() | |
class NumberNode(): | |
def __init__(self, c): | |
prefix = None | |
while True: | |
if not c.is_remains(): | |
raise | |
if c.s[0] == '+': | |
if prefix != '-': | |
prefix = '+' | |
c.advance(1) | |
elif c.s[0] == '-': | |
if prefix == '+': | |
prefix = '-' | |
else: | |
prefix = '+' | |
c.advance(1) | |
else: | |
break | |
i = 0 | |
while c.is_remains(i) and c.s[i].isdigit(): | |
i += 1 | |
if i == 0: | |
raise | |
self.n = float(c.s[:i]) | |
c.advance(i) | |
if prefix == '-': | |
self.n = -self.n | |
def calc(self): | |
return self.n | |
while True: | |
s = input("enter an expression: ") | |
c = Cursor(s) | |
try: | |
node = Node(c) | |
except: | |
print("the given expression is invalid, try again") | |
continue | |
print("the answer is", node.calc()) | |
print("") |
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