编译原理丨第七周 ——1000. 词法分析程序设计 **

Description

设一语言的关键词、运算符、分界符的个数与单词如下： 
struct { int number; string str[10]; } keywords={3,"int","main","return"} ; //关键词
struct { int number; string str[10]; } operators ={5,"+","*","=","+=","*="}; //运算符
struct { int number; string str[10]; } boundaries ={6,"(",")","{","}",",",";"} ; //分界符
struct { int number; string str[100];} identifieres={0}; //标识符
struct { int number; string str[100];} Unsigned_integer={0}; //无符号整数
以上类号分别为1~5，序号从0开始；
标识符是字母开头的字母数字串；常量为无符号整数；
用C++设计一程序实现词法分析。

Input

输入一程序，结束符用”#”；

Output

输出单词数对：<类号，序号>。 输出标识符表，用空格分隔； 输出无符号整数表，用空格分隔；

Sample Input

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main(){ int a=2,b=3;  return 2*b+a;}#

Sample Output

<1,1><3,0><3,1><3,2><1,0><4,0><2,2><5,0><3,4><4,1><2,2><5,1><3,5><1,2><5,0><2,1><4,1><2,0><4,0><3,5><3,3>identifieres:a bUnsigned_integer:2 3

Problem Source: 词法分析

编译原理西西里的题目，还是比较简单的，需要注意的是要用cin.get（ch），不然读不进空格

// Problem#: 20907// Submission#: 5186361// The source code is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License// URI: http://creativecommons.org/licenses/by-nc-sa/3.0/// All Copyright reserved by Informatic Lab of Sun Yat-sen University////  main.cpp//  cifa////  Created by xie on 2017/10/18.//  Copyright © 2017年 xie. All rights reserved.//#include <iostream>using namespace std;struct { int number; string str[10]; } keywords={3,"int","main","return"} ; //关键词struct { int number; string str[10]; } operators ={5,"+","*","=","+=","*="}; //运算符struct { int number; string str[10]; } boundaries ={6,"(",")","{","}",",",";"} ; //分界符struct { int number; string str[100];} identifieres={0}; //标识符struct { int number; string str[100];} Unsigned_integer={0}; //无符号整数void handle(string my_str){    string temp_int = "";//用来暂时存储无符号整数的一部分    string temp_word = "";//用来暂时存储字符串    for(int i = 0;i<my_str.size();++i)    {        if(my_str[i] == ' ' || my_str[i] == '\n')//空格与换行不用处理            continue;        //先处理分界符的情况        if(my_str[i] == '(')         {            cout<<"<3,0>";            continue;        }           if(my_str[i] == ')')         {            cout<<"<3,1>";            continue;        }        if(my_str[i] == '{')         {            cout<<"<3,2>";            continue;        }        if(my_str[i] == '}')         {            cout<<"<3,3>";            continue;        }        if(my_str[i] == ',')         {            cout<<"<3,4>";            continue;        }        if(my_str[i] == ';')         {            cout<<"<3,5>";            continue;        }        //再到运算符        if(my_str[i] == '=')        {            cout<<"<2,2>";            continue;        }        if(my_str[i] == '+' )        {            if(my_str[i+1] == '=')            {                cout<<"<2,3>";                continue;            }            else            {                cout<<"<2,0>";                continue;            }        }        if(my_str[i] == '*')        {            if(my_str[i+1] == '=')            {                cout<<"2,4";                continue;            }            else            {                cout<<"<2,1>";                continue;            }        }        //再到无符号整数        if(isdigit(my_str[i]))        {            temp_int += my_str[i];            if(isdigit(my_str[i+1]))//如果下一位还是数字的话，留到下一次再处理                continue;            else            {                bool flag = false;//判断数字在Unsigned_integer中是否已经存在                for(int j = 0;j < Unsigned_integer.number;++j)                {                    if(temp_int == Unsigned_integer.str[j])                    {                        cout<<"<5,"<<j<<">";                        temp_int = "";//记得复原temp_int                        flag = true;                        break;                    }                }                if(flag == false)                {                    cout<<"<5,"<<Unsigned_integer.number<<">";                    Unsigned_integer.str[Unsigned_integer.number++] = temp_int;                    temp_int = "";                                    }            }        }        if(isalpha(my_str[i]))        {            temp_word += my_str[i];            if(('a'<=my_str[i+1]&&my_str[i+1]<='z')||('A'<=my_str[i+1]&&my_str[i+1]<='Z'))            {                //cout<<endl<<my_str[i+1];                continue;            }            bool flag1 = false;            for(int j = 0;j<3;++j)//处理关键字            {                if(temp_word == keywords.str[j])                {                    cout<<"<1,"<<j<<">";                    flag1 = true;                    temp_word = "";                    break;                }            }            if(flag1) continue;                        bool flag = false;//处理标识符，过程与上面类似            for(int j = 0;j<identifieres.number;++j)            {                if(temp_word == identifieres.str[j])                {                    cout<<"<4,"<<j<<">";                    temp_word = "";                    flag = true;                    break;                }            }            if(!flag)            {                cout<<"<4,"<<identifieres.number<<">";                identifieres.str[identifieres.number++] = temp_word;                temp_word = "";                            }        }    }    cout<<endl;    cout<<"identifieres:";    if(identifieres.number == 0)        ;    else            for(int i = 0;i<identifieres.number;++i)            cout<<identifieres.str[i]<<" ";    cout<<endl;    cout<<"Unsigned_integer:";    if(Unsigned_integer.number == 0)        ;    else        for(int i = 0;i<Unsigned_integer.number;++i)            cout<<Unsigned_integer.str[i]<<" ";    cout<<endl;}int main(int argc, const char * argv[]) {        char temp_char;    string temp_string;        while(cin.get(temp_char) && temp_char != '#')        temp_string += temp_char;    //cout<<temp_string;    handle(temp_string);    return 0;}