基于C语言构造词法分析器+语法分析器完成编译原理实验

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已于 2024-03-22 14:32:09 修改

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文章标签： c语言

于 2021-06-24 16:41:56 首次发布

本文链接：https://blog.youkuaiyun.com/lovely__boy/article/details/118190523

版权

本文介绍了如何使用LL(1)分析法开发一个针对特定简单语言的词法分析器，实现对C/C++源程序的语法检查和结构分析。主要涉及词法分析和语法分析的实现，以及在VS2019开发环境中完成的实例。

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功能概述：
根据简单语言的词法和各单词符号种别码表，采用LL（1）分析法进行文法分析编写C或C++语言源程序，实现针对该简单语言的词法分析器，对词法分析程序所提供的单词序列进行语法检查和结构分析然后构造语法分析器。

所用知识：1.词法分析 2.语法分析
开发环境：VS2019

//main.c 主函数
#include<stdio.h>
#include<stdlib.h>
#include <iostream>
#include"def.h"
#include"funs.h"

using namespace std;
WORD scaner();
int main()
{
    int over = 1; WORD one = new Node;
    std::cout << "输入句子#号结束：";
    cin.getline(input,100);//scanf("%s",input);
    p_input = 0;
    cout << "输入的句子：";cout<<input<<"\n";
    fun(one);
    lr();
  
}

//funs.h文件  实现功能
void te(), fa(), ex(), st(), yu(), lr();
char ch, input[255] = "", token[255] = "";
int p_input, p_token, k = 0, legth = 0;
const char* rwtab[] = { "begin","if" ,"then","while","do","end","game over" };
LinkList * wd;
WORD scaner();

void fun(WORD one) {

    int over = 1;
    LinkList* head = (LinkList*)malloc(sizeof(LinkList));
    LinkList * q, * r;
    q = head; 
    head->next = NULL;
    r = head;
    wd = head; 
    while (over < 1000 && over != -1) {     
        one = scaner();
        LinkList *p = (LinkList*)malloc(sizeof(LinkList));
        p->num = one->typenum;
        p->w = one->word;
        p->next = NULL;
        q->next = p;
        q = p;
        if (one->typenum < 1000) std::cout << "(" << p->num << "," << p->w << ") ";
        over = one->typenum;
    }
    wd = head->next;
}
void ex() {
    te();
    while(wd->num==13||wd->num==14)
    {
        wd = wd->next;
        te();
    }
    return;
}

void fa() {
    if (wd->num == 10 || wd->num == 11) wd = wd->next;
    else if (wd->num == 27)
    {
        wd = wd->next;
        ex();
        if (wd->num == 28) wd = wd->next;
        else { std::cout << "\n)错误"; k = 1; }
    }
    else { std::cout << "\n表达式错误"; k = 1; } 
    return;
}

void te() {
    fa();
    while (wd->num==15||wd->num==16) 
    {
        wd = wd->next;
        fa();
    }
    return;
}

void st() {
    if (wd->num == 10)
    {
        wd = wd->next;
        if (wd->num == 18)
        {
            wd = wd->next;
            ex();

        }
        else { std::cout << "\n赋值号错误"; k = 1; }
    }
    else  {std::cout << "\n输出于醋错误"; k = 1;}
    return;
}
void yu() {
    st();
    while (wd->num==26)//;
    {
        wd = wd->next;
        st();
    
    }
    return;
}
void lr() {

    if (wd->num == 1)//begin
    {
        wd = wd->next;
        yu();
        if (wd->num == 6) //end
        {
            wd = wd->next;
            if ( k == 0) std::cout << "\nsuccess";

        }
        else { if (k != 1) std::cout << "\nend错误"; k = 1; }

    }
    else std::cout << "\nbegin错误";
    return;

}

char m_getch()
{
    ch = input[p_input];
    p_input = p_input + 1;
    return (ch);
}
void getbc()
{
    while (ch == ' ' || ch == 10)
    {
        ch = input[p_input];
        p_input = p_input + 1; //std::cout <<ch <<"//";
    }
}
void concat()
{
   
        token[p_token] = ch;
        p_token++;
        token[p_token] = '\0';
   
  
}
int letter()
{
    if (ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z')
        return 1;
    else
        return 0;
}
int digit()
{
    if (ch >= '0' && ch <= '9')
        return 1;
    else
        return 0;
}
int reserve()
{
    int i = 0;
    while (strcmp(rwtab[i], "game over"))
    {
        if (!strcmp(rwtab[i], token))
        {
            return i + 1;
        }
        i = i + 1;
    }
    return 10;
}
void retract()
{
    p_input = p_input - 1;
}
WORD scaner() {

    WORD myword = new Node; 
    //char* t = (char*)calloc(legth, sizeof(char));
    //for (int i = 0; i <= 255;i++)   token[i] = ' ';  
    p_token = 0;
    m_getch();
    getbc(); 
   
    if (letter())
    {
        //legth = 0;
        while (letter() || digit())
        {   
            //legth++;
            concat();
            m_getch();
           
        }   
        //char* t = (char*)malloc(legth * sizeof(char));
        retract();
       // for (int i = 0; i <= legth - 1; i++) { t[i] = token[i]; }
        myword->typenum = reserve();
        myword->word = token;
        return(myword);
    }

    else if (digit())
    {
        //legth = 0;
        while (digit())
        {
           // legth++;
            concat();
            m_getch();
            
        }
        retract();
        //char* t = (char*)malloc(legth * sizeof(char));  for (int i = 0; i <= legth - 1; i++) std::cout <<t[i]<<"+";
        //for (int i = 0; i <= legth-1; i++)  t[i] = token[i];
        myword->typenum = 11;
        myword->word = token;
        return(myword);
    }

    else switch (ch)
    {

    case '=':   m_getch();
        if (ch == '=')
        {
            myword->typenum = 25;
            myword->word = "==";
            return(myword);
        }
        retract();
        myword->typenum = 25;
        myword->word = "=";
        return(myword);
        break;
    case '+':   myword->typenum = 13;
        myword->word = "+";
        return(myword);
        break;
    case '-':   myword->typenum = 14;
        myword->word = "-";
        return(myword);
        break;
    case '*':   myword->typenum = 15;
        myword->word = "*";
        return(myword);
        break;
    case '/':   myword->typenum = 16;
        myword->word = "/";
        return(myword);
        break;
    case '(':   myword->typenum = 27;
        myword->word = "(";
        return(myword);
        break;

    case ')':   myword->typenum = 28;
        myword->word = ")";
        return(myword);
        break;
    case ':':  m_getch();
        if (ch == '=')
        {
            myword->typenum = 18;
            myword->word = ":=";
            return myword;
        }
        retract();
        myword->typenum = 17;
        myword->word = ":";
        return(myword);
        break;
    case ';':   myword->typenum = 26;
        myword->word = ";";
        return(myword);
        break;
    case '#':   myword->typenum = 0;
        myword->word = "#";
        return(myword);
        break;
    case '>':   m_getch();
        if (ch == '=')
        {
            myword->typenum = 24;
            myword->word = ">=";
            return(myword);
        }
        retract();
        myword->typenum = 23;
        myword->word = ">";
        return(myword);
        break;
    case '<':   m_getch();
        if (ch == '=')
        {
            myword->typenum = 22;
            myword->word = "<=";
            return(myword);
        }
        retract();
        myword->typenum = 20;
        myword->word = "<";
        return(myword);
        break;

    case '\0':   myword->typenum = 1000;
        myword->word = "OVER";
        return(myword);
        break;

    default:    myword->typenum = -1;
        myword->word = "ERROR";
        return(myword);
        break;
    }
}

//def.h文件 定义结构体
typedef struct {
    int typenum;
    char *word;
}Node,*WORD;

typedef struct HNode{
    struct HNode *next;
    int num;
    char* w;
}LinkList;