这里刚开始试用python的函数功能，可能把局部变量和全局变量给写乱了，后期交之前还想再优化的时候发现越改越乱，太真实的hhh

实验四：语法分析器1–预测分析器构造

实验目的: 通过编写一个预测分析器，掌握自上而下构造语法分析器的方法之一------预测分析法。

实验要求：

1、该语法分析器的任务如下：
（1）可识别程序代码中符合以下文法中的3-5个，返回该语句为何种语句，或提示出错
文法G1:
L→E
E→E=T|T
E→E+T|T
T→T-F|F
F→(E)|id

文法G2:
L→E
E→E=T|T
E→E*T|T
T→T/F|T%F|F
F→(E)|id

文法G3:
D→TL
T→int|flort
L→id R
R→,id R|ε

文法G4:
L →E;L|ε
E →TE’
E’→+TE’|-TE’|ε
T →FT’
T’→*FT’|/FT’|mod FT’|ε
F →(E)|id|num

文法G5:
stmt→if expr then stmt else stmt
|if expr then stmt
|other
（2）出错处理可自行设计,并添加在预测分析表中

测试用例：

#include <stdio.h>
#include  <math.h>
int main ( ) {int a,b,c,disc,x1,x2,p,q;
scanf("%lf%lf%lf",&a,&b,&c);
sqrt=(b*b)/（4*a*c)  disc=b+b-a+c;if (disc<0) p=2.0*a;else  p=-b/(2.0*a)printf("x1=%7.2f\nx2=%7.2f\n",x1,x2);          }return 0;
}

环境：python 2.7 IDE：pyCharm

实验代码

因为还是用了之前实验2,3的内容，所以list还是这些

# -*- coding: UTF-8 -*-
# 设置列表
list0 = ['IF', 11, 'THEN', 12, 'ELSE', 13, 'INT', 14, 'CHAR', 15, 'FOR', 16]
list1 = ['{', 90, '}', 91, '(', 92, ')', 93]
list2 = ['=', 21, '>=', 22, "==", 23, '+', 24,  '/', 25, '%', 26, '++', 27, '"', 28, ';', 29]    # 运算符
list4 = []    # 数字  动态添加
list5 = []    # 变量名  动态添加，检查是否存在

基本就是之前实验2的东西，作为一个分割函数

def splitfuc():list_fin = []list_temp = []fo = open("*****路径\\test3.txt", "r")str_1 = fo.readlines()fo.close()# print str_1for y in range(len(str_1)):list_temp = list_temp + str_1[y].split(' ')   # 突然发现这应该一句话就能解决hhhy = 0p = len(list_temp)# print list_tempwhile y < p:if list_temp[y] == '':del list_temp[y]p = p - 1else:y = y + 1# print list_tempfo = open("C:\\Users\\Launcher-Z\\Desktop\\3_output.txt", "w")# 开始从第一个单词循环j = 0k = 0# 开始遍历for idx in range(len(list_temp)):str_new = list_temp[idx]i = 0while i < len(str_new):if 'a' <= str_new[i] <= 'z' or 'A' <= str_new[i] <= 'Z':if i != len(str_new)-1:end = i + 1while end < len(str_new):if 'a' <= str_new[end] <= 'z' or 'A' <= str_new[end] <= 'Z' or '0' <= str_new[end] <= '9':end = end + 1else:end = end - 1breakif i != end:tmp = str_new[i:end+1]if tmp.upper() in list0:list_fin = list_fin + [tmp]fo.write(tmp)fo.write(' ')else:if tmp not in list5:list5.append(tmp)list5.append(50 + k)k = k + 1list_fin = list_fin + [tmp]fo.write(tmp)fo.write(' ')else:list_fin = list_fin + [tmp]fo.write(tmp)fo.write(' ')i = end + 1continueelse:tmp = str_new[i]if tmp not in list5:list5.append(tmp)list5.append(50 + k)k = k + 1list_fin = list_fin + [tmp]fo.write(tmp)fo.write(' ')else:list_fin = list_fin + [tmp]fo.write(tmp)fo.write(' ')i = end + 1continueelse:tmp = str_new[i]if tmp not in list5:list5.append(tmp)list5.append(50 + k)k = k + 1list_fin = list_fin + [tmp]fo.write(tmp)fo.write(' ')else:list_fin = list_fin + [tmp]fo.write(tmp)fo.write(' ')i = i + 1continueelse:if '0' <= str_new[i] <= '9':sum_1 = 0sum_2 = 0.0flg_num = 0x = 1while i < len(str_new):if '0' <= str_new[i] <= '9':if flg_num == 0:sum_1 = sum_1 * 10 + int(str_new[i])i = i + 1else:sum_2 = sum_2 + int(str_new[i]) * (0.1 ** x)x = x + 1i = i + 1else:if str_new[i] == '.':i = i + 1flg_num = 1if str_new[i] <= '0' or str_new[i] >= '9':list_fin = list_fin + [sum_1]fo.write(str(sum_1))fo.write('.')fo.write(str_new[i])fo.write(' ')num_end = ii = i + 1breakelse:continueelse:num_end = iif flg_num == 0:if sum_1 not in list4:list4.append(sum_1)list4.append(40 + j)j = j + 1list_fin = list_fin + [sum_1]fo.write(str(sum_1))fo.write(' ')breakelse:sum_2 = sum_2 + sum_1if sum_2 not in list4:list4.append(sum_2)list4.append(40 + j)j = j + 1list_fin = list_fin + [sum_2]fo.write(str(sum_2))fo.write(' ')breaki = num_end-1else:# = 与 ==if str_new[i] == '=':if str_new[i + 1] == '=':list_fin = list_fin + ['==']fo.write('==')fo.write(' ')i = i + 1else:list_fin = list_fin + ['=']fo.write('=')fo.write(' ')else:# < 与 <=if str_new[i] == '>':if str_new[i + 1] == '=':list_fin = list_fin + ['>=']fo.write('>=')fo.write(' ')i = i + 1else:list_fin = list_fin + ['>']fo.write('>')fo.write(' ')else:# + 与 ++if str_new[i] == '+':if str_new[i + 1] == '+':list_fin = list_fin + ['++']fo.write('++')fo.write(' ')i = i + 1else:list_fin = list_fin + ['+']fo.write('+')fo.write(' ')else:if str_new[i] == '/':list_fin = list_fin + ['/']fo.write('/')fo.write(' ')else:if str_new[i] == '%':list_fin = list_fin + ['%']fo.write('%')fo.write(' ')else:if str_new[i] == '"':list_fin = list_fin + ['"']fo.write('"')fo.write(' ')else:if str_new[i] == ';':list_fin = list_fin + [';']fo.write(';')fo.write(' ')else:if str_new[i] == '{':list_fin = list_fin + ['{']fo.write('{')fo.write(' ')else:if str_new[i] == '}':list_fin = list_fin + ['}']fo.write('}')fo.write(' ')else:if str_new[i] == '(':list_fin = list_fin + ['(']fo.write('(')fo.write(' ')else:if str_new[i] == ')':list_fin = list_fin + [')']fo.write(')')fo.write(' ')else:if str_new[i] == '\n':fo.write('\n')else:# 错误判断，一般就是符号错误，最多2个，看下一位'='判断if str_new[i] not in list2 and list1:if i != len(str_new) - 1:if str_new[i + 1] == '=':list_fin = list_fin + [str_new[i: i + 2]]fo.write(str_new[i: i + 2])fo.write(' ')i = i + 1else:list_fin = list_fin + [str_new[i]]fo.write(str_new[i])fo.write(' ')else:list_fin = list_fin + [str_new[i]]fo.write(str_new[i])fo.write(' ')i = i + 1return list_fin    # 分割函数

开始准备要用到的数据结构

stack = []    # 模拟的一个堆栈
# G3 文法分析表
dict_G3 = {'G3': ['int', 'float', ',', 'id', '#'],'D': ['B G', 'B G', 'err', 'err', 'err'],'B': ['int', 'float', 'err', 'err', 'err'],'G': ['err', 'err', 'id R', 'id R', 'err'],'R': ['err', 'err', ', id R', 'err', 'Null']
}
# G4 文法分析表
dict_G4 = {'G4': ['id', 'num', '(', '+', '-', '*', '/', 'mod', ';', ')', '#'],'L': ['E ; L', 'E ; L', 'E ; L', 'err', 'err', 'err', 'err', 'err', 'err', 'err', 'Null'],'E': ['T e', 'T e', 'T e', 'err', 'err', 'err', 'err', 'err', 'err', 'err', 'err'],'e': ['err', 'err', 'err', '+ T e', '- T e', 'err', 'err', 'err', 'Null', 'Null', 'err'],'T': ['F t', 'F t', 'F t', 'err', 'err', 'err', 'err', 'err', 'err', 'err', 'err'],'t': ['err', 'err', 'err', 'Null', 'Null', '* F t', '/ F t', 'mod F t', 'Null', 'Null', 'err'],'F': ['id', 'num', '( E )', 'err', 'err', 'err', 'err', 'err', 'err', 'err', 'err']
}
# G5 文法分析表1.0
dict_G5 = {'G5': ['if', 'else', 'then', 'string', '#'],'S': ['if E then S s', 'err', 'err', 'E', 'err'],'s': ['err', 'else S', 'err', 'err', 'Null'],'E': ['err', 'err', 'err', 'string', 'err']
}# 判断str的first是在哪个字典中，从而选择哪个函数进行预测分析
str_spl = splitfuc()
print str_spl  # 全局变量，处理后分隔好的list

接下去新建一个list用来保存这个语法允许的首个词是啥，不允许的就用err代替

# G3_check 处理
list_check_G3_first = []
for index in range(len(dict_G3['G3'])):list_check_G3_first = list_check_G3_first + [dict_G3['G3'][index]] #检查first的list_check,从而选择文法
for index in range(len(dict_G3['G3'])):if dict_G3['D'][index] == 'err':list_check_G3_first[index] = 'err'
# print 'xxxxxxxxxxx check_G3_first'
# print list_check_G3_first
# print 'xxxxxxxxxxx G3'
# print dict_G3['G3']# G4_check 处理
list_check_G4_first = []
for index in range(len(dict_G4['G4'])):list_check_G4_first = list_check_G4_first + [dict_G4['G4'][index]]  # 检查first的list_check,从而选择文法
for index in range(len(dict_G4['G4'])):if dict_G4['L'][index] == 'err':list_check_G4_first[index] = 'err'
# print 'xxxxxxxxxxx check_G4_first'
# print list_check_G4_first
# print 'xxxxxxxxxxx G4'
# print dict_G4['G4']# G5_check 处理
list_check_G5_first = []
for index in range(len(dict_G5['G5'])):list_check_G5_first = list_check_G5_first + [dict_G5['G5'][index]]  # 检查first的list_check,从而选择文法
for index in range(len(dict_G5['G5'])):if dict_G5['S'][index] == 'err':list_check_G5_first[index] = 'err'
# print 'xxxxxxxxxxx check_G5_first'
# print list_check_G5_first
# print 'xxxxxxxxxxx G5'
# print dict_G5['G5']

对G3文法的处理函数，应该是有史以来自己写代码时候注释最清楚的了hhh

def func_g3(str_spl):# 处理成输入符号----  w#  替换 非在 G3 内的终结符为    'id'  可以放在G3函数中 输入的东西为处理好的str_spl# 如果语句的首个词在list_check中，则选择那个文法的处理函数str_spl_cpy = []for index in range(len(str_spl)):str_spl_cpy = str_spl_cpy + [str_spl[index]]  # 复制listfor index in range(len(str_spl)):if str_spl[index] in dict_G3['G3']:continueelse:str_spl_cpy[index] = 'id'str_spl_cpy = str_spl_cpy + ['#']# cpy比原来的list中多了 # 其他的id什么的都 index 从原list中返回真实的print 'xxxxxxxxxxx spl_cpy'print str_spl_cpy# 开始遍历cpy的list，进行对stack的操作stack = ['#', 'D']    # 初始状态# for index in range(len(str_spl_cpy)):# print 'xxxxxxxxxxx test stack'# print dict_G3['D']# print dict_G3[stack[1]]# 开始循环# 1.查看栈顶元素# 2.目前的spl_cpy[index]在G3中的index_2是多少# 3.栈顶元素对应的list[index_2]（是否存在）如D[index_2]是‘B G’# 4.弹出栈顶，按空格分开反向入栈# 5.判断栈顶是否=spl_cpy[index] ----是则弹出栈顶元素并输出，index下一个；----不是则重复1-5# 可以打包成G3处理函数index = 0list_after_check = []# 开始循环，按照输入流中的一步一步走while str_spl_cpy[index] != '#':while stack[len(stack)-1] != str_spl_cpy[index]:   # 推进栈中更新list_temp = []if str_spl_cpy[index] in dict_G3['G3']:index_2 = dict_G3['G3'].index(str_spl_cpy[index])else:print 'error1 含有语法定义中未存在的元素'breakif dict_G3[stack[len(stack)-1]][index_2] != 'err':if dict_G3[stack[len(stack)-1]][index_2] == 'Null':print '***弹出了：', stack[len(stack) - 1]stack.remove(stack[len(stack) - 1])else:list_temp = dict_G3[stack[len(stack) - 1]][index_2].split(' ')list_temp.reverse()print 'temp\n', list_tempprint 'stack before \n', stackstack.remove(stack[len(stack) - 1])stack = stack + list_tempprint 'stack after\n', stackelse:print 'error1 含有语法定义中未存在的元素'breakprint '弹出了：', stack[len(stack)-1]print '是原来的：', str_spl[index]list_after_check = list_after_check + [str_spl[index]]stack.remove(stack[len(stack)-1])index = index + 1print '目前到达的输入流位置指向：', str_spl_cpy[index]# 输入流指针已经到了最后，开始清空堆栈里的东西while len(stack) > 1:index_2 = dict_G3['G3'].index(str_spl_cpy[index])if dict_G3[stack[len(stack) - 1]][index_2] != 'err':if dict_G3[stack[len(stack)-1]][index_2] == 'Null':print 'stack before \n', stackprint '弹出了：', stack[len(stack) - 1]stack.remove(stack[len(stack) - 1])print 'stack after\n', stackelse:print 'error2 没有按照语法'else:print 'error1 有语法定义中未存在的元素'print '这是语法G3，经过循环遍历之后的原来语句是：', list_after_check# G3函数结束

对G4文法的处理函数

def func_g4(str_spl):str_spl_cpy = []for index in range(len(str_spl)):str_spl_cpy = str_spl_cpy + [str_spl[index]]  # 复制listfor index in range(len(str_spl)):if str_spl[index] in dict_G4['G4']:continueelse:if isinstance(str_spl_cpy[index], int):str_spl_cpy[index] = 'num'else:if 'a' <= str_spl_cpy[index][0] <= 'z' or 'A' <= str_spl_cpy[index][0] <= 'Z':str_spl_cpy[index] = 'id'else:continuestr_spl_cpy = str_spl_cpy + ['#']# cpy比原来的list中多了 # 其他的id什么的都 index 从原list中返回真实的print 'xxxxxxxxxxx spl_cpy'print str_spl_cpy# 开始遍历cpy的list，进行对stack的操作stack = ['#', 'L']  # 初始状态# for index in range(len(str_spl_cpy)):# print 'xxxxxxxxxxx test stack'# print dict_G3['D']# print dict_G3[stack[1]]# 开始循环# 1.查看栈顶元素# 2.目前的spl_cpy[index]在G3中的index_2是多少# 3.栈顶元素对应的list[index_2]（是否存在）如D[index_2]是‘B G’# 4.弹出栈顶，按空格分开反向入栈# 5.判断栈顶是否=spl_cpy[index] ----是则弹出栈顶元素并输出，index下一个；----不是则重复1-5# 可以打包成G3处理函数index = 0flg = 0list_after_check = []# 开始循环，按照输入流中的一步一步走while str_spl_cpy[index] != '#':while stack[len(stack) - 1] != str_spl_cpy[index]:  # 推进栈中更新list_temp = []if str_spl_cpy[index] in dict_G4['G4']:index_2 = dict_G4['G4'].index(str_spl_cpy[index])else:print 'error1 含有语法定义中未存在的元素'flg = 1breakif dict_G4[stack[len(stack) - 1]][index_2] != 'err':if dict_G4[stack[len(stack) - 1]][index_2] == 'Null':print '遇到ε弹出了：', stack[len(stack) - 1]stack.remove(stack[len(stack) - 1])else:list_temp = dict_G4[stack[len(stack) - 1]][index_2].split(' ')list_temp.reverse()print 'temp\n', list_tempprint 'stack before \n', stackstack.remove(stack[len(stack) - 1])stack = stack + list_tempprint 'stack after\n', stackelse:print 'error1 含有语法定义中未存在的元素'flg = 1breakif flg == 1:breakprint '弹出了：', stack[len(stack) - 1]print '是原来的：', str_spl[index]list_after_check = list_after_check + [str_spl[index]]stack.remove(stack[len(stack) - 1])index = index + 1print '目前到达的输入流位置指向：', str_spl_cpy[index]print '目前的stack里面有：', stackprint '目前到达的输入流位置指向：', str_spl_cpy[index]print '目前的stack里面有：', stack# 输入流指针已经到了最后，开始清空堆栈里的东西if flg != 1:while len(stack) > 1:index_2 = dict_G4['G4'].index(str_spl_cpy[index])if dict_G4[stack[len(stack) - 1]][index_2] != 'err':if dict_G4[stack[len(stack) - 1]][index_2] == 'Null':print 'stack before \n', stackprint '遇到ε弹出了：', stack[len(stack) - 1]stack.remove(stack[len(stack) - 1])print 'stack after\n', stackelse:print 'error2 没有按照语法来写语句'flg = 1breakelse:flg = 1print 'error2 没有按照语法来写语句(末尾缺少 ; )'breakif flg != 1:print '这是语法G4，经过循环遍历之后的原来语句是：', list_after_checkelse:print '虽然开头对应了文法G4，但是他里面存在不符合文法的字符或中间没按照文法写'else:print '虽然开头对应了文法G4，但是他里面存在不符合文法的字符或中间没按照文法写'# G4函数结束

对G5文法的处理函数,后面堆栈操作基本都一个样，其实可以再写个堆栈操作函数的，那个时候怠惰了

def func_g5(str_spl):str_temp = ''list_temp_for_g5 = []str_spl_cpy = []for index in range(len(str_spl)):str_spl_cpy = str_spl_cpy + [str_spl[index]]  # 复制liststr_spl_cpy = str_spl_cpy + ['#']# 先拼接起来index = 0while str_spl_cpy[index] != '#':if str_spl_cpy[index] != 'if':if str_spl_cpy[index] != 'else':if str_spl_cpy[index] != 'then':str_temp = str_temp + str_spl_cpy[index]else:list_temp_for_g5 = list_temp_for_g5 + [str_temp]str_temp = ''list_temp_for_g5 = list_temp_for_g5 + ['then']else:list_temp_for_g5 = list_temp_for_g5 + [str_temp]str_temp = ''list_temp_for_g5 = list_temp_for_g5 + ['else']else:list_temp_for_g5 = list_temp_for_g5 + [str_temp]str_temp = ''list_temp_for_g5 = list_temp_for_g5 + ['if']index = index + 1list_temp_for_g5 = list_temp_for_g5 + [str_temp]while '' in list_temp_for_g5:list_temp_for_g5.remove('')print 'xxxxxxxxxxx list temp for g5'print list_temp_for_g5# 再替换str内容为string 准备处理str_spl_cpy = []for index in range(len(list_temp_for_g5)):str_spl_cpy = str_spl_cpy + [list_temp_for_g5[index]]  # 复制liststr_spl_cpy = str_spl_cpy + ['#']str_spl_cpy_g5 = []for index in range(len(str_spl_cpy)):str_spl_cpy_g5 = str_spl_cpy_g5 + [str_spl_cpy[index]]  # 复制listfor index in range(len(str_spl_cpy_g5)):if str_spl_cpy_g5[index] != 'if':if str_spl_cpy_g5[index] != 'else':if str_spl_cpy_g5[index] != 'then':if str_spl_cpy_g5[index] != '#':str_spl_cpy_g5.insert(index, 'string')str_spl_cpy_g5.remove(str_spl_cpy_g5[index + 1])# cpy比原来的list中多了 # 其他的id什么的都 index 从原list中返回真实的print 'xxxxxxxxxxx spl_cpy'print str_spl_cpyprint 'xxxxxxxxxxx spl_cpy_g5'print str_spl_cpy_g5# 开始遍历cpy的list，进行对stack的操作stack = ['#', 'S']  # 初始状态# 开始循环# 1.查看栈顶元素# 2.目前的spl_cpy[index]在G3中的index_2是多少# 3.栈顶元素对应的list[index_2]（是否存在）如D[index_2]是‘B G’# 4.弹出栈顶，按空格分开反向入栈# 5.判断栈顶是否=spl_cpy[index] ----是则弹出栈顶元素并输出，index下一个；----不是则重复1-5# 可以打包成G3处理函数index = 0flg = 0list_after_check = []# 开始循环，按照输入流中的一步一步走while str_spl_cpy_g5[index] != '#':while stack[len(stack) - 1] != str_spl_cpy_g5[index]:  # 推进栈中更新list_temp = []if str_spl_cpy_g5[index] in dict_G5['G5']:index_2 = dict_G5['G5'].index(str_spl_cpy_g5[index])else:print 'error1 含有语法定义中未存在的元素'flg = 1breakif dict_G5[stack[len(stack) - 1]][index_2] != 'err':if dict_G5[stack[len(stack) - 1]][index_2] == 'Null':print '遇到ε弹出了：', stack[len(stack) - 1]stack.remove(stack[len(stack) - 1])else:list_temp = dict_G5[stack[len(stack) - 1]][index_2].split(' ')list_temp.reverse()print 'temp\n', list_tempprint 'stack before \n', stackstack.remove(stack[len(stack) - 1])stack = stack + list_tempprint 'stack after\n', stackelse:print 'error1 含有语法定义中未存在的元素'flg = 1breakif flg == 1:breakprint '弹出了：', stack[len(stack) - 1]print '是原来的：', str_spl_cpy[index]list_after_check = list_after_check + [str_spl_cpy[index]]stack.remove(stack[len(stack) - 1])index = index + 1print '目前到达的输入流位置指向：', str_spl_cpy_g5[index]print '目前的stack里面有：', stackprint '目前到达的输入流位置指向：', str_spl_cpy_g5[index]print '目前的stack里面有：', stack# 输入流指针已经到了最后，开始清空堆栈里的东西if flg != 1:while len(stack) > 1:index_2 = dict_G5['G5'].index(str_spl_cpy_g5[index])if dict_G5[stack[len(stack) - 1]][index_2] != 'err':if dict_G5[stack[len(stack) - 1]][index_2] == 'Null':print 'stack before \n', stackprint '遇到ε弹出了：', stack[len(stack) - 1]stack.remove(stack[len(stack) - 1])print 'stack after\n', stackelse:print 'error2 没有按照语法来写语句'flg = 1breakelse:flg = 1print 'error2 没有按照语法来写语句(末尾缺少 ; )'breakif flg != 1:print '这是语法G5，经过循环遍历之后的原来语句是：', list_after_checkelse:print '虽然开头对应了文法G5，但是他里面存在不符合文法的字符或中间没按照文法写'else:print '虽然开头对应了文法G5，但是他里面存在不符合文法的字符或中间没按照文法写'# G5函数结束

判断哪个文法的函数

def choose_gn(str_spl):str_cpy_g3 = []str_cpy_g4 = []str_cpy_g3 = str_cpy_g3 + [str_spl[0]]str_cpy_g4 = str_cpy_g4 + [str_spl[0]]if str_cpy_g3[0] not in dict_G3['G3']:        # G3str_cpy_g3[0] = 'id'if isinstance(str_cpy_g4[0], int):            # G4str_cpy_g4[0] = 'num'else:if 'a' <= str_cpy_g4[0][0] <= 'z' or 'A' <= str_cpy_g4[0][0] <= 'Z':str_cpy_g4[0] = 'id'if str_spl[0] == 'if':func_g5(str_spl)else:if str_cpy_g3[0] in list_check_G3_first:func_g3(str_spl)else:if str_cpy_g4[0] in list_check_G4_first:func_g4(str_spl)else:print 'err3，目前没有文法匹配该语句'

最后执行

choose_gn(str_spl)

代码结束

问题讨论

本来还想再进一步对if else 语句中的嵌套语句做一个嵌套分析的难度应该也不大，但是最后就是越改越乱了

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