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简单算术运算解释器 [复制链接]

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发表于 2012-09-13 09:49 |只看该作者 |倒序浏览

实现一个简单语法语言的解释器。在运行时解释器每次输入一行语句，输出可能的输出。

# -*- coding: cp936 -*-
def Execute(strCodeLine, output):
local_vars = {}
all_input = (strCodeLine.strip()).split("\n")
all_input = [item.strip() for item in all_input]
for index, item in enumerate(all_input):
tmp_list = [i.strip() for i in item.split(" ")]
all_input[index] = ""
for i in tmp_list:
if i != "":
all_input[index] += i
all_input[index] += " "
all_input[index] = all_input[index].strip()
flag = 0
for every_input in all_input:
tmp = check_input(every_input, local_vars)
if tmp != -1:
result = calcu_every_input(every_input, local_vars, tmp)
if result == "error":
flag = -1
elif result != None:
output.append(str(result))
else:
flag = -1
return flag
def calcu_every_input(every_input, local_vars, type):
if type == 1:
output_var = [item.strip() for item in every_input.split()]
return local_vars[output_var[1]]
elif type == 2:
input_exp = every_input.split("=")
result = calcu_expression(input_exp[0], input_exp[1], local_vars)
if result == "error":
return "error"
local_vars[input_exp[0].strip()] = result
def calcu_expression(var, expression, local_vars):
symbol_stack = []
value_stack = []
legal_symbol = ['+', '-', '*', '/', '(', ')']
expression = expression.strip()
expression_list = expression.split(" ")
result = 0
str_tmp = ""
for index, item in enumerate(expression_list):
if item in local_vars:
str_tmp += str(local_vars[item])
elif item.isdigit():
str_tmp += item
elif item in legal_symbol:
str_tmp += item
try:
##分析这里的字符串使除数不能为0
sign = str_tmp.find("/")
if sign == 1:
leftSign = str_tmp.split("/")
if leftSign[1] != '0':
result = eval(str_tmp)
local_vars[var.strip()] = result
else:
return "error"
else:
result = eval(str_tmp)
local_vars[var.strip()] = result
except:
return "error"
return result
def veritfy_var(var):
if var == "print":
return -1
if ((var[0] >= 'A') and (var[0] <= 'Z')) or ((var[0] >= 'a') and (var[0] <= 'z')):
index = 1
while index < len(var):
if not (((var[index] >= 'A') and (var[index] <= 'Z'))
or ((var[index] >= 'a') and (var[index] <= 'z'))
or ((var[index] >= '0') and (var[index] <= '9'))):
return -1
return 0
def check_input(every_input, local_vars):
legal_symbol = ['+', '-', '*', '/', '(', ')']
index = every_input.find("print")
if index == 0:
output_var = [item.strip() for item in every_input.split(" ")]
if len(output_var) == 2:
if output_var[1] in local_vars:
return 1
else:
input_var = every_input.split("=")
input_var = [item.strip() for item in input_var]
if len(input_var) == 2:
if veritfy_var(input_var[0]) == -1:
return -1
if len(input_var[0]) == 1:
right_in_var = input_var[1].split(" ")
right_in_var = [item.strip() for item in right_in_var]
for item in right_in_var:
if (item in legal_symbol) or (item in local_vars) or item.isdigit():
return 2
return -1
def CheckVarValue(output, checkList, outputret, checkret):
if (output == checkList) and (outputret == checkret):
print "pass"
else:
print "error"
# 立即数赋值
def testcase01():
strCodeLine = """
a = 90
print a"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["90"], ret, 0)
# 赋值语句：立即数加运算
def testcase02():
strCodeLine = """
b = 2 + 7
print b"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["9"], ret, 0)
# 赋值语句：立即数减运算
def testcase03():
strCodeLine = """
c = 9 - 1
print c"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["8"], ret, 0)
# 赋值语句：立即数乘运算
def testcase04():
strCodeLine = """
d = 9 - 1
e = 3 * d
print d
print e"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["8", "24"], ret, 0)
# 赋值语句：立即数除运算
def testcase05():
strCodeLine = """
f = 24
g = f / 4
print g"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["6"], ret, 0)
# 赋值语句：变量运算
def testcase06():
strCodeLine = """
h = 2 * 3
i = h + h
print h
print i"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["6", "12"], ret, 0)
# 赋值语句：变量值更新
def testcase07():
strCodeLine = """
j = 2 * 3
j = j * j
print j"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["36"], ret, 0)
# 赋值语句：运算符优先级
def testcase08():
strCodeLine = """
a = 10 * 3
b = 8
print a
c = a + b
print b
e = a - 5 * b / 2 + 8
print c
print e"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["30", "8", "38", "18"], ret, 0)
# 赋值语句：括号的简单使用
def testcase09():
strCodeLine = """
a = 3
print a
b = 8
d = a - ( b - 4 )
print d"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["3", "-1"], ret, 0)
# 赋值语句：括号的使用
def testcase10():
strCodeLine = """
a = 3
print a
b = 8
c = a * b
d = a - ( c - 4 ) * b
print d"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["3", "-157"], ret, 0)
# 赋值语句：变量名区分大小写
def testcase11():
strCodeLine = """
a = 100
A = 200
print a
print A
c = A / a
print c"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["100", "200", "2"], ret, 0)
# 异常用例：变量使用之前必须初始化过
def TestCase_Error_1():
strCodeLine = """
a = 1
c = a + d
print a"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["1"], ret, -1)
# 异常用例：分隔符为多个空格
def TestCase_Error_2():
strCodeLine = """
q = 1 + 2
print q"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["3"], ret, 0)
# 异常用例：语句必须完整
def TestCase_Error_3():
strCodeLine = """
a = 1 +"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, [], ret, -1)
# 异常用例：左值必须为变量
def TestCase_Error_4():
strCodeLine = """
90 = a
print a"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, [], ret, -1)
# 异常用例：关键字与变量之间必须有分隔符
def TestCase_Error_5():
strCodeLine = """
a = 0
printa"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, [], ret, -1)
# 异常用例：运算中除0
def TestCase_Error_6():
strCodeLine = """
a = 0
b = 2
c = 3
c = b / a
print c
d = a / b
print d"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["3", "0"], ret, -1)
# 异常用例：变量名采用关键字
def TestCase_Error_7():
strCodeLine = """
print = 1
a = 3
print print"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, [], ret, -1)
# 异常用例：复杂程序
def testcase12():
strCodeLine = """
a = 10000
print a
b = a * a
c = c * 10
print c
e = 1000
a = a / e
print a
c = a
d = 1 + 10 + ( b / ( a * 10 ) )
print d
"""
output = []
ret = Execute(strCodeLine, output)
CheckVarValue(output, ["10000", "10", "1000011"], ret, -1)
def main():
testcase01()
testcase02()
testcase03()
testcase04()
testcase05()
testcase06()
testcase07()
testcase08()
testcase09()
testcase10()
testcase11()
TestCase_Error_1()
TestCase_Error_2()
TestCase_Error_3()
TestCase_Error_4()
TestCase_Error_5()
TestCase_Error_6()
TestCase_Error_7()
testcase12()
if __name__ == '__main__':
main()