编译原理实验-词法分析器（包含源码）

本实验是合肥工业大学编译原理实验的百年老题目，这里只提供实验1，若有需要2、3可以去博主的GitHub上面

链接

一、实验目的

通过本实验的编程实践，使学生了解词法分析的任务，掌握词法分析程序设计的原理和构造方法，使学生对编译的基本概念、原理和方法有完整的和清楚的理解，并能正确地、熟练地运用。

二、功能描述

1) 从文件中读入c语言源程序 2) 统计行数和列数用于错误单词的定位 3) 删除空格类字符，包括回车、制表符空格 4) 按拼写单词，并用（内码，属性）二元式表示 5) 如果发现错误则报告出错 6) 根据需要是否填写标识符表供以后各阶段使用 7) 识别注释 8) 可识别小数

三、程序结构设计

四、详细的算法描述

五、测试方法和结果

测试方法

(1). C语言源程序存放在test.txt文件里面，直接打开读取此文件。 (2).可以识别注释，不分析；可识别小数 (3).可以识别的错误有： 标识符不规范的命名方式，如数字开头； 连续的算数运算符连在一起,如+- 错误的关系运算符，如<< 一个数字里面出现两个小数点，如3.1.4 一些非法的输入。 测试样例： if i=0 then n++; //abc a <=3b%); 12.3 1.3.4 << 3+- 1 aa

测试结果

package bianYiYuanLi; import java.io.*; import java.util.*; public class work1 { static ArrayList<String> k=new ArrayList<String>(Arrays.asList("do","end","for","if","printf","scanf","then","while")); //关键字 static ArrayList<String> s=new ArrayList<String>(Arrays.asList(",",";","(",")","[","]")); //分界符 static ArrayList<String> a=new ArrayList<String>(Arrays.asList("+","-","*","/")); //算术运算符 static ArrayList<String> r=new ArrayList<String>(Arrays.asList("<","<=",">",">=","=","<>")); //关系运算符 static ArrayList<String> ci=new ArrayList<>(); //常数 static ArrayList<String> id=new ArrayList<>(); //标识符 static int hangX=1; //行 static int lieY=1; //列 //查找识别方法 static void searchDis(String str) { int i=0; //区分String的首符，1为字母，2为数字，3为其他 char ch=str.charAt(0); if ((ch>=65&&ch<=90)||(ch>=97&&ch<=122)) i=1; else if(ch>=48&&ch<=57) i=2; else i=3; //开始查找识别 if (i==1) { //首符是字母，查关键字和标识符 boolean find=k.contains(str); if(find==true) { //System.out.println(str+'\t'+'\t'+"(1,"+str+")"+'\t'+'\t'+"关键字"+'\t'+'\t'+"("+hangX+","+lieY+")"); System.out.printf("%-10s%-10s%-10s%-10s",str,"(1,"+str+")","关键字","("+hangX+","+lieY+")"); System.out.println(); } else { //不是关键字，查询标识符 find=id.contains(str); if(find==true) { //System.out.println(str+" (6,"+str+") "+"标识符"+" ("+hangX+","+lieY+")"); System.out.printf("%-10s%-10s%-10s%-10s",str,"(6,"+str+")","标识符","("+hangX+","+lieY+")"); System.out.println(); } else { //标识符表没有时，插入 //System.out.println(str+" (6,"+str+") "+"标识符"+" ("+hangX+","+lieY+")"); System.out.printf("%-10s%-10s%-10s%-10s",str,"(6,"+str+")","标识符","("+hangX+","+lieY+")"); System.out.println(); id.add(str); } } } else if(i==2) { //首符是数字,查常数 boolean find=ci.contains(str); if(find==true) { //System.out.println(str+" (5,"+str+") "+"常数"+" ("+hangX+","+lieY+")"); System.out.printf("%-10s%-10s%-10s%-10s",str,"(5,"+str+")","常数","("+hangX+","+lieY+")"); System.out.println(); } else { //不在常数表中，插入 //System.out.println(str+" (5,"+str+") "+"常数"+" ("+hangX+","+lieY+")"); System.out.printf("%-10s%-10s%-10s%-10s",str,"(5,"+str+")","常数","("+hangX+","+lieY+")"); System.out.println(); ci.add(str); } } else { //查分界符，算术、逻辑运算符 if(s.contains(str)) { System.out.printf("%-10s%-10s%-10s%-10s",str,"(2,"+str+")","分界符","("+hangX+","+lieY+")"); System.out.println(); } else if(a.contains(str)) { System.out.printf("%-10s%-10s%-10s%-10s",str,"(3,"+str+")","算术运算符","("+hangX+","+lieY+")"); System.out.println(); } else if(r.contains(str)) { System.out.printf("%-10s%-10s%-10s%-10s",str,"(4,"+str+")","关系运算符","("+hangX+","+lieY+")"); System.out.println(); } else { System.out.printf("%-10s%-10s%-10s%-10s",str,"Error","Error","("+hangX+","+lieY+")"); System.out.println(); } } } //分析串函数 static void analysisString(String str2) { String strNow=""; //当前识别的串 char ch1; for(int i=0;i<str2.length();i++) { ch1=str2.charAt(i); if(ch1==' ') continue; if((ch1>=65&&ch1<=90)||(ch1>=97&&ch1<=122)) { //识别字母 strNow+=ch1; i++; //超前搜索 do { ch1=str2.charAt(i); if((ch1>=65&&ch1<=90)||(ch1>=97&&ch1<=122)||(ch1>=48&&ch1<=57)) { strNow+=ch1; i++; } else break; }while(i<str2.length()); i--; //指针复位 searchDis(strNow); strNow=""; lieY++; continue; } else if(ch1>=48&&ch1<=57) { //识别数字 strNow+=ch1; i++; //超前搜索 //将后续如果是字母或者是数字全部加进去 while(i<str2.length()){ ch1=str2.charAt(i); if((ch1>=65&&ch1<=90)||(ch1>=97&&ch1<=122)||(ch1>=48&&ch1<=57)||ch1=='.') { strNow+=ch1; i++; } else break; } i--; //指针复位 //判断数字中是否有字母，有输出为error int j; boolean errorDone=false; //标志是否做出了出错判定 for(j=0;j<strNow.length();j++) { char ch2=strNow.charAt(j); if((ch2>=65&&ch2<=90)||(ch2>=97&&ch2<=122)) { System.out.printf("%-10s%-10s%-10s%-10s",strNow,"Error","Error","("+hangX+","+lieY+")"); System.out.println(); errorDone=true; break; } } //判断数字中有几个小数点，有两个及以上出error int m; boolean tag=false; //tag为true时，表示已经识别到一个小数点 for(m=0;m<strNow.length();m++) { char ch2=strNow.charAt(m); if(ch2=='.'&&tag) { if(!errorDone) { //由于上面已经输出error，下面就不用再输出 System.out.printf("%-10s%-10s%-10s%-10s",strNow,"Error","Error","("+hangX+","+lieY+")"); System.out.println(); } errorDone=true; break; } else if(ch2=='.'&&!tag) { //第一个小数点识别 tag=true; } } if(!errorDone) searchDis(strNow); strNow=""; lieY++; continue; } else { //识别其他 strNow+=ch1; if(s.contains(strNow)) { //识别为分界符 searchDis(strNow); strNow=""; lieY++; continue; } else if(a.contains(strNow)||r.contains(strNow)) { //识别为算术运算符或关系运算符 i++; //判断运算符后面是否是关系或算术运算符，是则继续添加到strNow中 while(i<str2.length()) { ch1=str2.charAt(i); if(a.contains(ch1+"")||r.contains(ch1+"")) { strNow+=ch1; i++; } else break; } searchDis(strNow); i--; //复位 strNow=""; lieY++; continue; } else { //识别非法字符 searchDis(strNow); strNow=""; lieY++; continue; } } } } //主函数 public static void main(String[] args) { try { RandomAccessFile inF=new RandomAccessFile("test.txt","r"); String str1=null; while((str1=inF.readLine())!=null) { //一行一行的读取 //删除注释 for(int i=0;i<str1.length()-1;i++) { if(str1.charAt(i)=='/'&&str1.charAt(i+1)=='/') { str1=str1.substring(0, i); break; } } analysisString(str1); //调用分析函数 hangX++; //行加1 lieY=1; //列置1 } inF.close(); } catch(IOException e) { System.out.println(e); } } }