编译原理-词法分析

学生实验报告实验项目名称：词法分析实验学时：同组学生姓名：实验地点：实验日期：实验成绩：批改教师：批改时间：一、实验目的和要求通过编写并上机调试一个词法分析程序，掌握在对程序设计语言的源程序进行扫描的过程中，将其分解后各类单词的词法分析方法。

二、实验仪器和设备硬件：PC机软件：Visual Studio 2005工具三、实验过程输入：从具有代表性的高级程序设计语言中，选取一个适当大小的子集，例如可以选取一类典型单词，也可以尽可能使各种类型的单词都能兼顾到。

输出：单词串的输出形式，所输出的每一单词均按形如（字符类型单词和其它字符<行，列>）的三元式编码。

字符类型包括关键字、标识符、浮点数、指数形式、常数、引入文件、分隔符。

<行，列>标识单词及各个字符在文本框中出现的位置。

词法规则∙关键字: 本程序识别的关键字为int real if then else while ，仅当单独出现以上标识符时识别为关键字，对于inta,ifb等识别为标识符。

∙标识符: 一个标识符必须以字母开头，后面接上字母和数字，否则产生报错信息，程序停止词法分析，输出相关错误信息如: 正确：abc, abc123, 等，错误：123abc∙操作符: 本程序识别的操作符为: + - / * = == < <= > >= != & ^ | && || ? &= |= ^= ++ -- += -= /= *= <<= << >>= >> % %= 当！后跟其它字符时产生出错信息。

∙分隔符: 本程序识别的分隔符为: ( ) { } ; : , [ ] “∙数字: 识别的数字遵循以下文法规则:digit ←0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9intnumber ← digit+exponent ←(E|e) ( + | - | ε ) digit+fraction ← . digit+realnumber ← digit+ exponent | digit+ fraction ( exponent | ε )例如：正确: 123, 123E2, 123.3123.3E4错误: 123A，123E, 123.A . 123.3A, 123.3E∙注释符: 本程序对// /**/三者的注释符均识别.∙引入文件为#include<**>形式，其他做出错处理设计思路本程序采用字符流形式读入文件，识别其中的关键字，标识符，分隔符，注释符，引入文件声明等.设计了一个灵活的读取字符的自动机为如下图所显示词法分析部分的Lexical类如下:using System;using System.IO;using System.Collections;namespace Lexical_Analyzer{public class Lexical{private int rnum;//行号private int rpos;//列号private static ArrayList symbolTable;private StreamReader br;private char c;private char bC;private int state;private String str;private int a = 0;private static string[] str1={"bool","break","case","char","do","double","else","main","false","float","for","if","int", "long","main","new","null","private","protected","public","static","true","try","typeof","un it","void","while","return","short","sizeof","switch","console","write","string","length"};public Lexical(StreamReader br){symbolTable = new ArrayList();this.br = br;c = ' ';bC = ' ';state = 0;rnum = 1;rpos = 0;str = "";}public ArrayList getSymbolTable(){c = nextChar();state = 0;analyzer();return symbolTable;}private void analyzer(){bool isRunning = true;while (isRunning){switch (state){case 0:if (c == ' ' || (int)c == 13) //空格{}else if (c == '\t') //tab{rpos += 3;}else if ((int)c == 10) //回车{rnum++;}else if (c == '~') //结束符{return;}else if (c == '"'){install("分隔符", c.ToString(), rpos, rnum); }else if (c.ToString() == "'"){install("分隔符", c.ToString(), rpos, rnum); }else if (c == '+') //操作符+{state = 15;//install("操作符","+",rpos,rnum);}else if (c == '-') //操作符-{state = 14;//install("操作符","-",rpos,rnum);}else if (c == '/') //操作符/{state = 1;}else if (c == '*') //操作符*{state = 16;//install("操作符","*",rpos,rnum);}else if (c == '=') //操作符={state = 2;}else if (c == '<') //操作符<{state = 3;}else if (c == '>') //操作符>{}else if (c == '!') //操作符!{state = 5;}else if (c == '?')//操作符？{state = 19;}else if (c == '%'){state = 17;}else if (c == '&'){state = 18;}else if (c == '|'){state = 20;}else if (c == '^'){state = 21;}else if (c == '{' || c == '}' || c == '[' || c == ']' || c == '(' || c == ')' || c == ':' || c == ';' || c == ',') //分隔符{install("分隔符", c.ToString (), rpos, rnum);}else if ((int)c == 65535){isRunning = false;}else if (isLetter(c)) //读到了字符{bC = c;state = 6;}else if (isDigit(c)) //读到了数字符{bC = c;str = "";}else if (c == '#'){state = 13;}else{state = 0;isRunning = false;fail(0);}c = nextChar();break;case 1:if (c == '='){state = 0;install("操作符", "/=", rpos - 1, rnum);c = nextChar();}else if (c == '/') //表示注释后面的东西,不读它 {while ((int)c != 10)//回车{c = nextChar();}rpos = 0; //从下一行开始rnum++;c = nextChar();state = 0;}else if (c == '*'){char b = ' ';while (c != '/')//回车{b = c;c = nextChar();}if (b == '*'){c = nextChar();state = 0;}}else{state = 0; // 下一个不是/, 后退一步到state=0 install("操作符", "/", rpos - 1, rnum);}break;case 2:if (c == '=') //表示操作符=={state = 0;install("操作符", "==", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "=", rpos - 1, rnum);}break;case 3:if (c == '<') //表示操作符<<{state = 0;install("操作符", "<<", rpos - 1, rnum);c = nextChar();if (c == '='){state = 0;install("操作符", "<<=", rpos - 1, rnum);c = nextChar();}}else if (c == '=') //表示操作符<={state = 0;install("操作符", "<=", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "<", rpos - 1, rnum);}break;case 4:if (c == '>') //表示操作符>>{state = 0;install("操作符", ">>", rpos - 1, rnum);c = nextChar();if (c == '='){state = 0;install("操作符", ">>=", rpos - 1, rnum);c = nextChar();}}else if (c == '=') //表示操作符>={state = 0;install("操作符", ">=", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", ">", rpos - 1, rnum);}break;case 5:if (c == '=') // 表示操作符!={state = 0;install("操作符", "!=", rpos - 1, rnum);c = nextChar();}else{state = 0;isRunning = false;fail(1);}break;//***********************************//读入标识符,后面是数字符和字母才是对的//***********************************case 6:String id = "" + bC;if (c != '[' && c != ']'){while ((isLetter(c) || isDigit(c)) && c != '[' && c != ']') {id += c;c = nextChar();}if (isKey(id))install("关键字", id, rpos - id.Length, rnum);elseinstall("标识符", id, rpos - id.Length, rnum);if (c == '.'){install("分隔符", c.ToString(), rpos - id.Length, rnum);c = nextChar();}state = 0;}else{install("标识符", id, rpos - id.Length, rnum);state = 0;}break;//*********************************************//读入数字符,后面是数字符(循环); .(转状态);E(转状态)//**********************************************case 7:str += bC;if (c != ']'){while (isDigit(c) && c != ']'){str += c;c = nextChar();}if (c == ']'){install("数字符", str, rpos - str.Length, rnum); }else if (c == '.'){state = 8;c = nextChar();}else if (c == 'E' || c == 'e'){if (c == 'e')a = 1;state = 10;c = nextChar();}//需要判断是否是 11w等else if (isLetter(c)){state = 0;isRunning = false;fail(4);}else{state = 0;install("数字符", str, rpos - str.Length, rnum); }}else{state = 0;install("数字符", str, rpos - str.Length, rnum);}break;//***********************************// " ." 后面跟的字符,除了数字符其它都出错//***********************************case 8:str += '.';if (isDigit(c)){state = 9;str += c;}else{state = 0;isRunning = false;fail(2);}break;//***********************************************************************************// ".数字符" 后面字符,可以是数字符或者是E(需要加错误提示,当不是空格而是其他字母时候)//************************************************************************************case 9:while (isDigit(c)){str += c;c = nextChar();}if (c == 'E' || c == 'e'){if (c == 'e')a = 1;state = 10;c = nextChar();}//需要判断是否是 11w 等else if (isLetter(c)){state = 0;isRunning = false;fail(2);}else{state = 0;install("浮点数", str, rpos - str.Length, rnum);}break;//*********************************************// "E" 后面字符, "+";"-";"数字符" 都是对的,其他都是错的//********************************************case 10:if (a == 1)str += 'e';elsestr += 'E';if (c == '+' || c == '-'){state = 11;str += c;c = nextChar();}else if (isDigit(c)){state = 12;str += c;c = nextChar();}else{state = 0;isRunning = false;fail(2);}break;//*****************************************// "+" "-" 后面字符, 数字符是对的.其他都是错的//*****************************************case 11:if (isDigit(c)){state = 12;str += c;c = nextChar();}else{state = 0;isRunning = false;fail(2);}break;//***********************************// "E数字符" 后面字符,只有数字符是对的//*********************************case 12:while (isDigit(c)){str += c;c = nextChar();}if (isLetter(c)){state = 0;isRunning = false;fail(2);}install("指数形式", str, rpos - str.Length, rnum);state = 0;break;case 13: //声明部分id = "#";while (isLetter(c)){id += c;c = nextChar();}if (id == "#include" && c == '<'){id += c;c = nextChar();while (isLetter(c) || this.isDigit(c)||c=='.'){id += c;c = nextChar();}if (c == '>'){id += c;install("文件引入", id, rpos - id.Length, rnum);c = nextChar();}elsefail(3);}elsestate = 0;break;case 14: // 表示操作符-=或--或-if (c == '='){state = 0;install("操作符", "-=", rpos - 1, rnum);c = nextChar();}else if (c == '-'){state = 0;install("操作符", "--", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "-", rpos - 1, rnum); }break;case 15: // 表示操作符+=或++或+if (c == '='){state = 0;install("操作符", "+=", rpos - 1, rnum);c = nextChar();}else if (c == '+'){state = 0;install("操作符", "++", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "+", rpos - 1, rnum); }break;case 16: // 表示操作符*=if (c == '='){install("操作符", "*=", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "*", rpos - 1, rnum);c = nextChar();}break;case 17:if (c == '=')//表示操作符%={state = 0;install("操作符", "%=", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "%", rpos - 1, rnum);c = nextChar();}break;case 18:if (c == '='){state = 0;install("操作符", "&=", rpos - 1, rnum);c = nextChar();}else if (c == '&'){state = 0;install("操作符", "&&", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "&", rpos - 1, rnum);c = nextChar();}break;case 19:if (c == '：') // 表示操作符？：{state = 0;install("操作符", "？：", rpos - 1, rnum);c = nextChar();}else{state = 0;isRunning = false;fail(1);}break;case 20:if (c == '='){state = 0;install("操作符", "|=", rpos - 1, rnum);c = nextChar();}else if (c == '|'){state = 0;install("操作符", "||", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "|", rpos - 1, rnum);c = nextChar();}break;case 21:if (c == '='){state = 0;install("操作符", "^=", rpos - 1, rnum);c = nextChar();}else{state = 0;install("操作符", "^", rpos - 1, rnum);c = nextChar();}break;}}}private void fail(int i){string typeerror = ""; ;switch (i){case 0:typeerror = "输入非法字符错误";break;case 1:typeerror = "操作符错误";break;case 2:typeerror = "数字符错误";break;case 3:typeerror = "声明错误";break;case 4:typeerror = "标识符错误";break;}Console.Write(typeerror + ",位置<" + rnum + "," + rpos + ">");}private char nextChar(){char t;rpos++;//列if (br.Peek() == -1){br.Close();return'~';}t = (char)br.Read();return t;}private void install(String tType, String aValue, int rpos, int rnum){ArrayList tokenArray = new ArrayList();tokenArray.Add(tType);tokenArray.Add(aValue);tokenArray.Add("<" + rnum.ToString() + "," + rpos.ToString() + ">");symbolTable.Add(tokenArray);ArrayList tempArray = tokenArray;for (int j = 0; j < tempArray.Count; j++){Console.Write(tempArray[j].ToString() + " ");}Console.WriteLine();str = "";}private bool isLetter(char checkChar){int checkInt = (int)checkChar;if ((checkInt <= 122 && checkInt >= 97) || (checkInt >= 65 && checkInt <= 97)) {return true;}return false;}private bool isDigit(char checkChar){int checkInt = (int)checkChar;if (checkInt <= 57 && checkInt >= 48){return true;}return false;}private bool isKey(String checkKey){for (int i = 0; i < str1.Length; i++){if (checkKey.Equals(str1[i])){return true;}}return false;}}}四、实验结果与分析1、对程序的基本词法分析main(){a=1;if(a==1)then a=2.3;else a=3;}图12、变量命名标准识别标识符以字母开头，以下程序将产生错误main(){int 12a=123;if(a==1)then a=2.3;else a=3;}图23、数字识别main(){int a=123;float a=3.1514;if(a==1)then a=2.3;else a=3a;}由词法规则可得”3a”为错误的数字表示形式，可识别浮点数，输入信息如下：图34、头文件的识别#include<stdio.h>main(){int a=123;if(a!1)then a=2.3;else a=3;}图45、注释的识别对//、/*/两种注释的识别main(){int a=123;/ghfhgh/if(a!1)then a=2.3;else a=3;/*jkhjkhjh*/ }图56、数组的识别main(){string a[]={"a"}}这块程序代码实现了数组的表示识别图6五、实验心得。