【编译原理】词法分析器

发布时间:2023年12月27日

【编译原理】词法分析器

实验要求:

设置一个名字表NameL和常数表ConstL,当遇到标识符时,将其字符串送入名字表NameL,并把其名字表地址作为标识符的语义Seman值。常数情形也一样,不要求翻译成二进制数。要求在NameL和ConstL表中没有相同元素,同时具有简单的错误处理功能(找出源程序中所有存在的词法错误并指出错误所在的行数)。试用高级程序设计语言编写一个针对下述单词集的词法分析器。

token表

在这里插入图片描述

评分标准

①是否使用文件输入、输出;
②是否可以查找多个错误;
③每个错误是否有错误提示,包括错误所在行、错误信息;
④错误提示信息是否区分不同类别;
⑤同名标识符或常数是否重复存放;
⑥是否正确建立单词表和名字表、常量表的链接;
⑦是否处理注释。

词法分析器

import re


class MyToken:
    def __init__(self, MyType, seman, MyStr):
        self.MyType = MyType
        self.seman = seman
        self.MyStr = MyStr

    def __str__(self):
        s = self.MyStr.replace('\n','')
        return "token.class:  {:5}\t\tstr:  {:10}\tseman:\t{} \t".format(self.MyType, s, self.seman)


# 单词集状态列表
states = ['if', 'else', 'for', 'while', 'break', 'return', 'continue', 'float', 'int', 'char', '标识符',
          '正整数、正实数、零', '+', '-',
          '*', '/', '%', '>', '>=', '<', '<=', '!=', '==', '!', '&', '|', ',', '=', '[', ']', '(', ')', '{', '}', ';',
          '.', '\\', '#']
choiceStatec = [13, 14, 15, 16, 17, 18, 20, 24, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36]  # 用于防止while循环中出现多次elif
inputs = []  # 输入的字符


tokens = []  # 单词表
NameL = []  # 名字表
ConstL = []  # 常数表



i = 0
line = 1



# 将文件内容提取到inputs
def codeToInputs(sourceCodes):
    for line in sourceCodes:
        for char in line:
            inputs.append(char)
            if char == '#':
                return


# 判断是否为字母
def isLetter(char):
    pattern = r"[a-zA-Z]"
    return bool(re.match(pattern, char))


# 判断是否为数字
def isDigit(char):
    pattern = r"[0-9]"
    return bool(re.match(pattern, char))


# 普通的字符识别
def isC(char, state):
    tokens.append(MyToken(state, "^", char))


def choiceState(char):  # 选择单字符对应状态
    state = 0
    if char in states:
        for k in range(len(states)):
            if states[k] == char:  # 判断单个字符
                if char in ['>', '<', '!', '=', '&', '|', '\\'] and inputs[i] in ['=', '&', '|', 'n']:  # 如果是双字符
                    state = 19
                else:
                    state = k + 1
    else:
        state = 0
    return state


def error():
    print(f"第{line}行---未知字符错误")


# 词法分析
def nextToken():
    global i
    global line
    name = ""
    char = inputs[i]
    i += 1
    while char == ' ' or char == '\n' or char == '\t':  # 如果是空就跳过
        if char == '\n':
            line += 1
        char = inputs[i]
        i += 1
        if char == '#':
            i -= 1
    global state
    state = 0
    while True:

        if state == 0:  # 选择
            if char == '#':
                i -= 1
                state = 38
                continue
            if char == '/' and (inputs[i] == '/' or inputs[i] == '*'):  # 注释
                state = 42
                continue
            if choiceState(char) != 0:  # 判断后面的单字符,获取状态
                state = choiceState(char)
                i -= 1
                continue
            if char == "i":
                state = 1
            elif char == "e":
                state = 2
            elif char == 'f':
                state = 3
            elif char == 'w':
                state = 4
            elif char == 'b':
                state = 5
            elif char == 'r':
                state = 6
            elif char == 'c':
                state = 7
            elif isDigit(char):  # 数字
                state = 12
            elif isLetter(char):  # 字符串
                i -= 1
                state = 11

            else:
                error()  # 非法字符报错
                i -= 1
                state = 38
        elif state == 1:  # if

            if inputs[i] == 'f':  # 判断第二个是否为f
                if isDigit(inputs[i + 1]) or isLetter(inputs[i + 1]):  # 标识符
                    i -= 1
                    state = 11
                else:
                    m = MyToken(1, "^", "if")  # 在单词表和名字表加入
                    tokens.append(m)
                    state = 38

            elif inputs[i] == 'n':  # 判断第二个是否为n
                i += 1
                if inputs[i] == 't':
                    if isDigit(inputs[i + 1]) or isLetter(inputs[i + 1]):  # 标识符
                        i -= 2
                        state = 11
                    else:
                        m = MyToken(9, "^", "int")  # 在单词表和名字表加入
                        tokens.append(m)
                        state = 38
                else:
                    if isDigit(inputs[i]) or isLetter(inputs[i]):  # 标识符
                        i -= 2
                        state = 11
                    else:
                        m = MyToken(11, "^", "in")  # 在单词表和名字表加入
                        tokens.append(m)
                        state = 38
                        i -= 1
            else:  # 以i开头的标识符
                i -= 1
                state = 11

        elif state == 2:  # else
            if ''.join(inputs[i:i + 3]) == 'lse':
                if isDigit(inputs[i + 3]) or isLetter(inputs[i + 3]):
                    i -= 1
                    state = 11
                else:
                    m = MyToken(2, "^", "else")  # 在单词表和名字表加入
                    tokens.append(m)
                    state = 38
                    i += 2
            else:
                i -= 1
                state = 11

        elif state == 3:  # for

            if inputs[i] == 'o':
                if inputs[i + 1] == 'r':
                    if isDigit(inputs[i + 2]) or isLetter(inputs[i + 2]):
                        i -= 1
                        state = 11
                    else:
                        m = MyToken(3, "^", "for")  # 在单词表和名字表加入
                        tokens.append(m)
                        state = 38
                        i += 1
                else:
                    i -= 1
                    state = 11
            elif inputs[i] == 'l':
                if "".join(inputs[i:i + 4]) == 'loat':
                    if isDigit(inputs[i + 4]) or isLetter(inputs[i + 4]):
                        i -= 1
                        state = 11
                    else:
                        m = MyToken(8, "^", "float")  # 在单词表和名字表加入
                        tokens.append(m)
                        state = 38
                        i += 3
                else:
                    i -= 1
                    state = 11
            else:
                i -= 1
                state = 11

        elif state == 4:  # while
            if "".join(inputs[i:i + 4]) == 'hile':
                if isDigit(inputs[i + 4]) or isLetter(inputs[i + 4]):
                    i -= 1
                    state = 11
                else:
                    m = MyToken(4, "^", "while")  # 在单词表和名字表加入
                    tokens.append(m)
                    state = 38
                    i += 3
            else:
                i -= 1
                state = 11


        elif state == 5:  # break
            if "".join(inputs[i:i + 4]) == 'reak':
                if isDigit(inputs[i + 4]) or isLetter(inputs[i + 4]):
                    i -= 1
                    state = 11
                else:
                    m = MyToken(5, "^", "break")  # 在单词表和名字表加入
                    tokens.append(m)
                    state = 38
                    i += 3
            else:
                i -= 1
                state = 11

        elif state == 6:  # return
            if "".join(inputs[i:i + 5]) == 'eturn':
                if isDigit(inputs[i + 5]) or isLetter(inputs[i + 5]):
                    i -= 1
                    state = 11
                else:
                    m = MyToken(6, "^", "return")  # 在单词表和名字表加入
                    tokens.append(m)
                    state = 38
                    i += 4
            else:
                i -= 1
                state = 11

        elif state == 7:  # continue
            if inputs[i] == 'o':
                if "".join(inputs[i + 1:i + 7]) == 'ntinue':
                    if isDigit(inputs[i + 7]) or isLetter(inputs[i + 7]):
                        i -= 1
                        state = 11
                    else:
                        m = MyToken(7, "^", "continue")  # 在单词表和名字表加入
                        tokens.append(m)
                        state = 38
                        i += 6
                else:
                    i -= 1
                    state = 11

            elif inputs[i] == 'h':
                if "".join(inputs[i + 1:i + 3]) == 'ar':
                    if isDigit(inputs[i + 3]) or isLetter(inputs[i + 3]):
                        i -= 1
                        state = 11
                    else:
                        m = MyToken(10, "^", "char")  # 在单词表和名字表加入
                        tokens.append(m)
                        state = 38
                        i += 2
                else:
                    state = 11
                    i -= 1
            else:
                i -= 1
                state = 11
        elif state == 11:  # 标识符
            char = inputs[i]
            i += 1
            name += char
            if isLetter(char):
                state = 39
            else:
                state = 40

        elif state == 12:

            name += char
            char = inputs[i]
            if isDigit(inputs[i]):  # 判断数字
                i += 1
                state = 12
            else:
                if inputs[i] == ' ' or inputs[i] == '\n' or inputs[i] == '\t' or inputs[i] == '#':

                    flag = 0
                    index = -1
                    for ii in range(len(ConstL)):
                        if ConstL[ii].MyStr == name:
                            flag = 1
                            index = ii
                    if flag == 1:
                        tokens.append(MyToken(12, index, name))

                    else:
                        ConstL.append(MyToken(12, len(ConstL), name))
                        tokens.append(MyToken(12, len(ConstL)-1, name))

                else:
                    print(f"第{line}行---标识符错误")
                    char = inputs[i]
                    while char != ' ' and char != '\t' and char != '\n' and char != '#':
                        i += 1
                        char = inputs[i]
                state = 38
                i -= 1

        elif state == 19:  # 处理双字符
            m = ""
            if inputs[i] == '>' and inputs[i + 1] == '=':
                m = MyToken(19, "^", ">=")
            if inputs[i] == '<' and inputs[i + 1] == '=':
                m = MyToken(21, "^", "<=")
            if inputs[i] == '!' and inputs[i + 1] == '=':
                m = MyToken(22, "^", "!=")
            if inputs[i] == '=' and inputs[i + 1] == '=':
                m = MyToken(23, "^", "==")
            if inputs[i] == '&' and inputs[i + 1] == '&':
                m = MyToken(25, "^", "&&")
            if inputs[i] == '|' and inputs[i + 1] == '|':
                m = MyToken(26, "^", "||")
            if inputs[i] == '\\' and inputs[i + 1] == 'n':
                m = MyToken(37, "^", "\\n")
            tokens.append(m)
            i += 1
            return

        elif state == 38:  # 文件结束
            return
        elif state == 39:  # 处理标识符
            char = inputs[i]
            i += 1
            if char == '#':
                i -= 1
                state = 40
                continue

            if isDigit(char) or isLetter(char):
                state = 39
                if char != '\n':
                    name += char
                else:
                    line += 1

            else:  # 不是字母和数字,就不是标识符了
                state = 40
        elif state == 40:
            flag = 0
            index = -1
            for ii in range(len(NameL)):
                if NameL[ii].MyStr == name:
                    flag = 1
                    index = ii
            if flag == 1:
                tokens.append(MyToken(11, index, name))

            else:
                NameL.append(MyToken(11, len(NameL), name))
                tokens.append(MyToken(11, len(NameL)-1, name))


            i -= 2  # 外面的while+1,所以这里要-1
            if char == '#':
                i += 1
            try:
                if states.index(char) and char != '#':  # 如果有字符
                    name = name[:-1]
                    state = 41

            except:
                pass
            return
        elif state == 41:
            st = states.index(char)
            isC(char, st)
            i -= 1
            return
        elif state == 42:  # 处理注释 // /**/
            if inputs[i] == '/':  # //注释
                i += 1
                char = inputs[i]
                while char != '\n':
                    i += 1
                    char = inputs[i]
                i += 1
                state = 0
            pass
        elif state in choiceStatec:
            isC(states[state - 1], state)  # 普通的字符识别
            return
        else:
            pass


# 从文件读取内容
def readSourceCode(read_path):
    with open(read_path, "r") as file:
        lines = file.readlines()
    return lines

# def sort_by_type(token):
#     return token.MyType


# 将单词表输出到文件
def writeTokens(tokens,Name,Const):
    with open("tokens.txt", "w") as file:
        for token in tokens:
            file.write(f"{token}\n")
    with open("NameL.txt","w") as file:
        for n in Name:
            file.write(str(n)+"\n")
    with open("ConstL.txt", "w") as file:
        for c in Const:
            file.write(str(c)+"\n")

if __name__ == '__main__':
    read_path = 'source_code.txt'
    sourceCodes = readSourceCode(read_path)
    codeToInputs(sourceCodes)
    while inputs[i] != '#':
        nextToken()
        i += 1
    tokens.append(MyToken(38, "^", "#"))  # 最后一个
    writeTokens(tokens,NameL,ConstL)




"""
设置一个名字表NameL和常数表ConstL,当遇到标识符时,将其字符串送入名字表NameL,并把其名字表地址作为标识符的语义Seman值。
常数情形也一样,不要求翻译成二进制数。
要求在NameL和ConstL表中没有相同元素,同时具有简单的错误处理功能(找出源程序中所有存在的词法错误并指出错误所在的行数)。
试用高级程序设计语言编写一个针对下述单词集的词法分析器
"""
# 单词       编码  语义
# if         1     空(^)
# else       2     空(^)
# for        3     空(^)
# while      4     空(^)
# break      5     空(^)
# return     6     空(^)
# continue   7     空(^)
# float      8     空(^)
# int        9     空(^)
# char       10    空(^)
# 标识符      11    名字表地址
# 正整数      12    常数表地址
# 正实数      12    常数表地址
# 零         12    常数表地址
# +          13    空(^)
# -          14    空(^)
# *          15    空(^)
# /          16    空(^)
# %          17    空(^)
# >          18    空(^)
# >=         19    空(^)
# <          20    空(^)
# <=         21    空(^)
# !=         22    空(^)
# ==         23    空(^)
# !          24    空(^)
# &&         25    空(^)
# ||         26    空(^)
# ,          27    空(^)
# =          28    空(^)
# [          29    空(^)
# ]          30    空(^)
# (          31    空(^)
# )          32    空(^)
# {          33    空(^)
# }          34    空(^)
# ;          35    空(^)
# .          36    空(^)
# 换行符      37    空(^)
# 文件结束    38    空(^)

运行

首先创建:source_code.txt

123 456 123
while ( i < 0 )
    if i > 1
        return
    else
        i += 1
for ( int i = 0 ; i <= 3 ; i += 1 )
    flag += 1
    if flag == 10
        continue
int j = 0 ;
#

执行后,会在同目录下生成三个文件:
tokens.txt、NameL.txt、ConstL.txt

token.txt内容如下:
在这里插入图片描述

文章来源:https://blog.csdn.net/qq_61839115/article/details/135241434
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