编译原理（四）之解析语言翻译成三地址代码

选择部分C语言的语法成分，设计其词法语法语义分析程序。

设计并实现一个一遍扫描的词法语法语义分析程序，将部分C语言的语法成分翻译成三地址代码，要求有一定的出错提示和错误恢复功能。

例如简单赋值语句：

area=3.14*a*a;
s= 2*3.1416*r*(h+r);

翻译成后缀式：

area 3.14 a * a * =
s 2 3.1416 *r*h r +*=

翻译成三地址代码：

t1=3.14*a;
t2=t1*a;
area=t2;
t3=2*3.1416;
t4=t3*r;
t5=h+r;
t6=t4*t5;
s=t6;

源程序：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace CLanguage {class CLanguage {WordStream wordStream = new WordStream("text.txt");// List<Error> errors = new List<Error>();static void Main(string[] args) {CLanguage syntax = new CLanguage();syntax.SemanticsParser();Console.ReadKey();}/// <summary>/// 语义分析/// </summary>public void SemanticsParser() {do {functionParser();} while(wordStream.ReadNextWord().typeNum != WordPicker.endTypeNumber);if(success) {// Console.WriteLine("成功");foreach(FourFormula f in list) {Console.WriteLine(f);}Console.WriteLine("---finish---");}}/// <summary>/// 函数/// </summary>private void functionParser() {Word word = wordStream.ReadNextWord();//返回类型if(!KeyWords.isReturnType(word)) {addError(word, "返回值错误");}word = wordStream.ReadNextWord();//函数名if(!isIdentifier(word)) {addError(word, "函数名错误");}//（参数）{word = wordStream.ReadNextWord();if(word.typeNum != Symbols.left_bracket.typeNum) {addError(word, "(缺失");wordStream.retractWord();}arguments();word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_bracket.typeNum) {addError(word, ")缺失");wordStream.retractWord();}word = wordStream.ReadNextWord();if(word.typeNum != Symbols.left_curly_bracket.typeNum) {addError(word, "{缺失");wordStream.retractWord();}//语句串statementSequence();//}word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_curly_bracket.typeNum) {addError(word, "}缺失");wordStream.retractWord();}}/// <summary>/// 参数/// </summary>private void arguments() {Word word = wordStream.ReadNextWord();if(!KeyWords.isType(word)) {if(isIdentifier(word))addBeforeError(word, "参数类型缺失");else {if(wordStream.LastWord().typeNum == Symbols.comma.typeNum)addBeforeError(word, ",多余");wordStream.retractWord();return;}}word = wordStream.ReadNextWord();if(!isIdentifier(word)) {addBeforeError(word, "参数标识符错误");if(word.typeNum == Symbols.right_bracket.typeNum) {wordStream.retractWord();return;}}//逗号word = wordStream.ReadNextWord();if(word.typeNum == Symbols.comma.typeNum) {arguments();}else if(word.typeNum == Symbols.right_bracket.typeNum) {wordStream.retractWord();return;}}/// <summary>/// 判断是否是标识符/// </summary>/// <param name="word"></param>/// <returns></returns>private bool isIdentifier(Word word) {return word.typeNum == WordPicker.identifierTypeNumber;}/// <summary>/// 语串/// </summary>private void statementSequence() {Word word = wordStream.ReadNextWord();while(word.typeNum != Symbols.right_curly_bracket.typeNum && word.typeNum != WordPicker.endTypeNumber) {statement(word);word = wordStream.ReadNextWord();}wordStream.retractWord();}/// <summary>/// 语句/// </summary>/// <param name="word"></param>private void statement(Word word) {if(KeyWords.isType(word)) {defineStatement();}else if(isIdentifier(word)) {assignStatement();}else if(KeyWords.isIfCondition(word)) {ifCondition();}/*else if(KeyWords.isForLoop(word)) {forLoop();}*/else if(KeyWords.isWhileLoop(word)) {whileLoop();}else {addError(word, "多余");}}#region IF语句块/// <summary>/// if条件语句/// </summary>private void ifCondition() {//(Word word = wordStream.ReadNextWord();if(word.typeNum != Symbols.left_bracket.typeNum) {addError(word, "(缺失");wordStream.retractWord();}List<FourFormula> trueList = new List<FourFormula>();List<FourFormula> falseList = new List<FourFormula>();condition(trueList, falseList);//)word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_bracket.typeNum) {addError(word, ")缺失");wordStream.retractWord();}backPatch(trueList, getNextCodeLine());//回填true分支地址word = wordStream.ReadNextWord();if(word.typeNum == Symbols.left_curly_bracket.typeNum) {//语句块statementSequence();word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_curly_bracket.typeNum) {addBeforeError(word, "缺少右花括号");wordStream.retractWord();}}else {statement(word);}FourFormula f=addFourFormula();//true分支结束跳转backPatch(falseList, getNextCodeLine());//回填false分支地址elseCondition();//else语句backPatch(f, getNextCodeLine());}/// <summary>/// else语句/// </summary>private void elseCondition() {Word word = wordStream.ReadNextWord();if(word.typeNum != KeyWords.ELSE.typeNum) {wordStream.retractWord();return;}word = wordStream.ReadNextWord();if(word.typeNum == Symbols.left_curly_bracket.typeNum) {statementSequence();word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_curly_bracket.typeNum) {addBeforeError(word, "缺少右花括号");wordStream.retractWord();}}else {statement(word);}}#endregion/// <summary>/// for循环/// </summary>private void forLoop() {}/// <summary>/// while循环/// </summary>private void whileLoop() {//(Word word = wordStream.ReadNextWord();if(word.typeNum != Symbols.left_bracket.typeNum) {addError(word, "(缺失");wordStream.retractWord();}int startCode = getNextCodeLine();List<FourFormula> trueList = new List<FourFormula>();List<FourFormula> falseList = new List<FourFormula>();condition(trueList, falseList);//)word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_bracket.typeNum) {addError(word, ")缺失");wordStream.retractWord();}backPatch(trueList, getNextCodeLine());//回填true分支地址word = wordStream.ReadNextWord();if(word.typeNum == Symbols.left_curly_bracket.typeNum) {//语句块statementSequence();word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_curly_bracket.typeNum) {addBeforeError(word, "缺少右花括号");wordStream.retractWord();}}else {statement(word);}Word w = new Word();w.word = "" + startCode;addFourFormula(w, null, null, null);backPatch(falseList, getNextCodeLine());}/// <summary>/// 条件语句/// </summary>private void condition(List<FourFormula> trueList, List<FourFormula> falseList) {boolExpressStatement(trueList, falseList);}/// <summary>/// 获取下一行地址编号/// </summary>/// <returns></returns>private int getNextCodeLine() {return list.Count;}/// <summary>/// 回填跳转位置/// </summary>/// <param name="size"></param>private void backPatch(List<FourFormula> indexs, int row) {foreach(FourFormula f in indexs) {f.result = new Word();f.result.word = "" + row;// getNextLine();}indexs.Clear();}private void backPatch(FourFormula f, int row) {f.result = new Word();f.result.word = "" + row;}/// <summary>/// 定义语句/// </summary>private void defineStatement() {Word word = wordStream.ReadNextWord();if(!isIdentifier(word)) {addBeforeError(word, "变量名缺失");wordStream.retractWord();}word = wordStream.ReadNextWord();if(word.typeNum == Symbols.assign.typeNum) {addFourFormula(wordStream.LastWord(), expressStatement(), null, null);word = wordStream.ReadNextWord();}if(word.typeNum == Symbols.comma.typeNum) {defineStatement();}else if(word.typeNum != Symbols.semicolon.typeNum) {addBeforeError(word, ";缺失");wordStream.retractWord();}}/// <summary>/// 赋值语句/// </summary>private void assignStatement() {Word result = wordStream.NowWord();Word word = wordStream.ReadNextWord();if(word.typeNum != Symbols.assign.typeNum) {addBeforeError(word, "=缺失");wordStream.retractWord();}Word arg1 = expressStatement();addFourFormula(result, arg1, null, null);word = wordStream.ReadNextWord();if(word.typeNum != Symbols.semicolon.typeNum) {addBeforeError(word, ";缺失");wordStream.retractWord();}}#region 表达式解析/// <summary>/// 表达式/// </summary>private Word expressStatement() {Word express, arg1, arg2;       arg1 = express = term();          Word word = wordStream.ReadNextWord();while(word.typeNum == Symbols.add.typeNum|| word.typeNum == Symbols.sub.typeNum) {arg2 = term();express = createTempVar();express = createTempVar();addFourFormula(express, arg1, arg2, word);arg1 = express;word = wordStream.ReadNextWord();}wordStream.retractWord();return express;}/// <summary>/// 项/// </summary>/// <returns></returns>private Word term() {Word term, arg1, arg2;       term = factor();arg1 = term;Word word = wordStream.ReadNextWord();while(word.typeNum == Symbols.mul.typeNum|| word.typeNum == Symbols.except.typeNum|| word.typeNum == Symbols.remain.typeNum) {arg2 = factor();term = createTempVar();addFourFormula(term, arg1, arg2, word);arg1 = term;word = wordStream.ReadNextWord();}wordStream.retractWord();return term;}/// <summary>/// 表达式因子/// </summary>private Word factor() {Word factor = null;Word word = wordStream.ReadNextWord();if(isValue(word)) {factor = word;}else if(word.typeNum == Symbols.left_bracket.typeNum) {factor = expressStatement();word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_bracket.typeNum) {addBeforeError(word, ")缺失");wordStream.retractWord();}}else {addBeforeError(word, "表达式错误");wordStream.retractWord();//throw new Exception(); }return factor;}#endregion#region 布尔表达式/// <summary>/// 表达式/// </summary>private void boolExpressStatement(List<FourFormula> trueList, List<FourFormula> falseList) {boolTerm(trueList, falseList);Word word = wordStream.ReadNextWord();while(word.typeNum == Symbols.logic_or.typeNum) {backPatch(falseList, getNextCodeLine());boolTerm(trueList, falseList);                               word = wordStream.ReadNextWord();}wordStream.retractWord();}/// <summary>/// 项/// </summary>/// <returns></returns>private void boolTerm(List<FourFormula> trueList, List<FourFormula> falseList) {boolFactor(trueList, falseList);Word word = wordStream.ReadNextWord();while(word.typeNum == Symbols.logic_and.typeNum) {backPatch(trueList, getNextCodeLine());boolFactor(trueList, falseList);word = wordStream.ReadNextWord();}wordStream.retractWord();}/// <summary>/// 表达式因子/// </summary>private void boolFactor(List<FourFormula> trueList, List<FourFormula> falseList) {Word word = wordStream.ReadNextWord();if(isValue(word)) {wordStream.retractWord();boolRelation(trueList,falseList);             }else if(word.typeNum == Symbols.left_bracket.typeNum) {if(isExpress()) {wordStream.retractWord();boolRelation(trueList, falseList);}else {boolExpressStatement(trueList, falseList);word = wordStream.ReadNextWord();if(word.typeNum != Symbols.right_bracket.typeNum) {addBeforeError(word, ")缺失");wordStream.retractWord();}}}else if(word.typeNum == Symbols.logic_not.typeNum) {boolExpressStatement(falseList,trueList);}else{addBeforeError(word, "布尔表达式错误");wordStream.retractWord();//throw new Exception(); }}private bool isExpress() {int left = 1;int right = 0;int words = 1;Word word = wordStream.ReadNextWord();while(Symbols.isExpressSymbol(word)) {if(word.typeNum == Symbols.left_bracket.typeNum) {left++;}else if(word.typeNum == Symbols.right_bracket.typeNum) {right++;}word = wordStream.ReadNextWord();words++;}wordStream.retractWord(words);return left==right;}/// <summary>/// 关系表达式或布尔值/// </summary>/// <param name="trueList"></param>/// <param name="falseList"></param>private void boolRelation(List<FourFormula> trueList, List<FourFormula> falseList) {Word word = expressStatement();Word word2 = null;Word op = wordStream.ReadNextWord();if(Symbols.isCompareOperator(op)) {word2 = expressStatement();if(word2 == null) {return ;}}else{wordStream.retractWord();op = new Word();}            FourFormula f = addFourFormula(null, word, word2, op);trueList.Add(f);f = addFourFormula();falseList.Add(f);}#endregion/// <summary>/// 判断是否是数值变量类型/// </summary>/// <param name="word"></param>/// <returns></returns>private bool isValue(Word word) {return word.typeNum == WordPicker.numberTypeNumber|| word.typeNum == WordPicker.identifierTypeNumber|| word.typeNum == WordPicker.charTypeNumber|| word.typeNum == WordPicker.stringTypeNumber;}#region 添加四元式List<FourFormula> list = new List<FourFormula>();/// <summary>/// 保存四元式/// </summary>private FourFormula addFourFormula(Word result, Word arg1, Word arg2, Word op) {FourFormula fourFormula = new FourFormula();fourFormula.result = result;fourFormula.arg1 = arg1;fourFormula.arg2 = arg2;fourFormula.operate = op;fourFormula.codeRow = list.Count;list.Add(fourFormula);return fourFormula;}private FourFormula addFourFormula() {FourFormula fourFormula = new FourFormula();fourFormula.codeRow = list.Count;list.Add(fourFormula);return fourFormula;}#endregionint idNameCount = 0;/// <summary>/// 创建临时变量/// </summary>/// <returns></returns>public Word createTempVar() {Word word = new Word();word.word = "$T" + idNameCount++;word.typeNum =WordPicker.tempValTypeNumber;return word;}#region 输出错误bool success = true;//语法解析结果/// <summary>/// 输出在特定之前的错误/// </summary>/// <param name="word"></param>/// <param name="v"></param>private void addBeforeError(Word word, string v) {success = false;Console.WriteLine("error:" + word.ToPositionInfo() + "\t在该字之前" + v);}/// <summary>/// 输出错误/// </summary>/// <param name="word"></param>/// <param name="v"></param>private void addError(Word word, string v) {success = false;Console.WriteLine("error:" + word.ToPositionInfo() + "\t" + v);}#endregion}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace CLanguage {/// <summary>/// 四元式/// </summary>class FourFormula {public int codeRow;public Word result;public Word arg1;public Word operate;public Word arg2;public override string ToString() {string s = "(" + codeRow + ") ";//赋值if(result.typeNum>0) {s = s + result.word + " = " + arg1.word;if(operate != null) {s +=" "+ operate.word;}if(arg2 != null) {s += " " + arg2.word;}}else if(operate == null) {//直接跳转s += "goto (" + result.word + ")";}else {//条件跳转s = s + "if " + arg1.word;if(operate.word!=null) {s += " " + operate.word + " " + arg2.word;}s += "  goto (" + result.word + ")";}return s;}}}

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;namespace CLanguage {/// <summary>/// 词/// </summary>class Word {public int typeNum=0;public string word;public int col=0;public int row=0;public override string ToString() {return "(" + typeNum + "," + word + ")";}public string ToPositionInfo() {return "行:"+(row+1)+"\t列:"+col+"\t码:"+typeNum + "\t字:" + word;}}class WordPicker {string[] input;//int input_index = 0;int row = 0;int col = 0;char character;/// <summary>/// 操作符表/// </summary>    string[] operatorSort = null;public static int identifierTypeNumber;    //变量名类型public static int numberTypeNumber;        //数值类型public static int charTypeNumber;          //字符类型public static int stringTypeNumber;        //字符串类型public static int endTypeNumber = -1;      //结束符类型public static int errorTypeNumber = -2;    //出错类型public static int noDefine = -3;           //未定义类型public static char nullChar = '\0';public static int tempValTypeNumber;      //临时变量类型public WordPicker(string file) {input= File.ReadAllLines(file);           identifierTypeNumber = KeyWords.keyWordTable.Length+1;numberTypeNumber = KeyWords.keyWordTable.Length + 2;charTypeNumber = KeyWords.keyWordTable.Length + 3;stringTypeNumber = KeyWords.keyWordTable.Length + 4;tempValTypeNumber= KeyWords.keyWordTable.Length + 5;operatorSort = new string[Symbols.operatorTable.Length];Array.Copy(Symbols.operatorTable, operatorSort, Symbols.operatorTable.Length);Array.Sort(operatorSort);Array.Reverse(operatorSort);}/// <summary>/// 读词/// </summary>/// <returns></returns>public Word Scanner() {Word myWord;          read();readValidChar();//标识符if(char.IsLetter(character)) {myWord=readWord();}//数值else if(char.IsDigit(character)) {myWord = readDigit();}//字符常量else if(character == '\'') {myWord = readConstChar();}//字符串else if(character == '\"') {myWord = readConstString();}/*//结束符else if(character == endChar) {myWord.word = "" + endChar;myWord.typeNum = endTypeNumber;}*///空值else if(character == nullChar) {myWord = new Word();myWord.row = row;myWord.col = col;myWord.word = "Ending";myWord.typeNum = endTypeNumber;}//其他字符else {myWord = readOtherChar();}return myWord;}/// <summary>/// 标识符/// </summary>/// <param name="myWord"></param>private Word readWord() {Word myWord = new Word();myWord.row = row;myWord.col = col;while(char.IsLetter(character) || char.IsDigit(character)) {myWord.word += character;read();}retract();myWord.typeNum = KeyWords.getTypeNumber(myWord.word);return myWord;}/// <summary>/// 其他字符/// </summary>/// <param name="myWord"></param>private Word readOtherChar() {Word myWord = new Word();myWord.row = row;myWord.col = col;string s = "" + character;for(int i = 0; i < 2; i++) {read();if(character == nullChar) {break;}s += character;}foreach(string op in operatorSort) {if(s.StartsWith(op)) {retract(s.Length - op.Length);s = op;break;}}myWord.word = s;myWord.typeNum = Symbols.getTypeNumber(myWord.word);return myWord;}/// <summary>/// 识别数字常量/// </summary>/// <param name="myWord"></param>private Word readDigit() {Word myWord = new Word();myWord.row = row;myWord.col = col;while(char.IsDigit(character)) {myWord.word += character;read();}if(character == '.') {myWord.word += character;read();while(char.IsDigit(character)) {myWord.word += character;read();}}retract();myWord.typeNum = numberTypeNumber;return myWord;}/// <summary>/// 识别字符常量/// </summary>/// <param name="myWord"></param>private Word readConstChar() {Word myWord = new Word();myWord.row = row;myWord.col = col;// myWord.word = "" + character;read();//读取直到'\''结束while(character != '\'') {myWord.word += character;read();//读到空字符或结束字符if(character == nullChar /*|| character == endChar*/|| char.IsControl(character)) {/* if(character == endChar) {myWord.word +=endChar;} */myWord.typeNum = errorTypeNumber;return myWord;}}// myWord.word += character;Match r = Regex.Match(myWord.word, "^(\\\\([0-7]{1,3}|x[0-9a-fA-F]+|[abfnrtv\\\\\'\"?])|[^\\\\])$");//转义字符模式匹配if(!r.Success) {myWord.typeNum = errorTypeNumber;return myWord;}myWord.typeNum = charTypeNumber;return myWord;}/// <summary>/// 识别常量字符串/// </summary>/// <param name="myWord"></param>private Word readConstString() {Word myWord = new Word();myWord.row = row;myWord.col = col;// myWord.word = "" + character;read();while(character != '\"') {myWord.word += character;read();//读到空字符或结束字符if(character == nullChar || char.IsControl(character)) {// myWord.word += "0";myWord.typeNum = errorTypeNumber;return myWord;}}// myWord.word += character;//转义字符模式匹配if(!isLegalString(myWord.word)) {myWord.typeNum = errorTypeNumber;return myWord;}myWord.typeNum = stringTypeNumber;return myWord;}/// <summary>/// 合法字符串书写/// </summary>/// <param name="word"></param>/// <returns></returns>private bool isLegalString(string word) {int i = 0;while(i < word.Length) {if(word[i] == '\\') {if(++i == word.Length)return false;foreach(char c in translateChar) {if(c == word[i]) {goto aLabel;}}return false;}aLabel:i++;}return true;}const string translateChar = "abfnrtv\\\'\"?";const string realChar = "\a\b\f\n\r\t\v\\\'\"?";/// <summary>/// 转换为真实字符串/// </summary>/// <param name="word"></param>/// <returns></returns>private string toRealString(string word) {string res = "";int index;for(int i = 0; i < word.Length; i++) {if(word[i] == '\\') {if(++i == word.Length)throw new Exception("字符串以\\结尾异常");index = translateChar.IndexOf(word[i]);if(index == -1)throw new Exception("\\" + word[i] + "解析异常");res += realChar[index];}else {res += word[i];}}return res;}/// <summary>/// 读一个字符/// </summary>void read() {if(input.Length <= row|| input.Length == row+1 && input[input.Length-1].Length<=col) {character = '\0';}else {if(col >= input[row].Length) {col = 0;row++;}character = input[row][col];col++;}}/// <summary>/// 去除无效字符/// </summary>void readValidChar() {while(char.IsWhiteSpace(character)) {if(character == '\0') {return;}read();              }//判断注释if(character == '/' && input[row].Length > col) {ignoreNote();}}/// <summary>/// 忽视注解/// </summary>private void ignoreNote() {read();//注释‘//’if(character == '/') {row++;col = 0;                              read();readValidChar();}//注释‘/*。。。*/’else if(character == '*') {read();if(character == '\0') {return;}char c;while(true) {c = character;read();if('*' == c && '/' == character) {read();readValidChar();return;}if(character == '\0') {return;}                }}else {retract();}}/// <summary>/// 回退一个字符/// </summary>void retract() {            col=col-2;checkCol();read();}/// <summary>/// 回退v个字符/// </summary>/// <param name="v"></param>private void retract(int v) {if(v == 0)return;col = col - v - 1;checkCol();read();}/// <summary>/// 检查col是否合法/// </summary>void checkCol() {if(col < 0) {row--;col = input[row].Length + col;checkCol();}}}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;namespace CLanguage {class KeyWords {/// <summary>/// 关键字表/// </summary>public static string[] keyWordTable = {"auto","break","case", "char","const","continue","default","do","double","else","enum","extern","float","for","goto","if", "int","long", "register","return","short","signed","sizeof","static","struct","switch","typedef","union","unsigned","void","volatile","while"};public static Word AUTO, BREAK, CASE, CHAR, CONST,CONTINUE, DEFAULT, DO, DOUBLE,ELSE, ENUM, EXTERN, FLOAT, FOR,GOTO, IF, INT, LONG, REGISTER,RETURN, SHORT, SIGNED, SIZEOF, STATIC,STRUCT, SWITCH, TYPEDEF, UNION, UNSIGNED,VOID, VOLATILE, WHILE;static KeyWords() {Type t = typeof(KeyWords);FieldInfo[] fields = t.GetFields();Word word;foreach(FieldInfo f in fields)if(f.FieldType.Equals(typeof(Word))) {word = new Word();word.word = f.Name.ToLower();word.typeNum = getTypeNumber(word.word);f.SetValue(t, word);}}/// <summary>/// 获取关键字编码/// </summary>/// <returns></returns>public static int getTypeNumber(string s) {for(int i = 0; i < keyWordTable.Length; i++) {if(keyWordTable[i] == s) {return i+1;}}return WordPicker.identifierTypeNumber;}public static bool isPrefType(Word w) {return SIGNED.typeNum == w.typeNum|| UNSIGNED.typeNum == w.typeNum;}public static bool isType(Word w) {return INT.typeNum == w.typeNum|| CHAR.typeNum == w.typeNum|| DOUBLE.typeNum == w.typeNum|| FLOAT.typeNum == w.typeNum|| SHORT.typeNum == w.typeNum;               }public static bool isReturnType(Word w) {return isType(w) || VOID.typeNum == w.typeNum;}internal static bool isIfCondition(Word word) {return word.typeNum == IF.typeNum;}internal static bool isForLoop(Word word) {return word.typeNum == FOR.typeNum;}internal static bool isWhileLoop(Word word) {return word.typeNum == WHILE.typeNum;}internal static bool isDoLoop(Word word) {return  word.typeNum == DO.typeNum;}internal static bool isKeyWord(Word word) {return word.typeNum > 0 && word.typeNum <= keyWordTable.Length;}}class Symbols {public static string[] operatorTable = {"{","}","[","]","(",")","->",".","++","--","!","&&","||","~","&","|","^","+","-","*","/","%","<<",">>","<",">",">=","<=","==","!=","?",":",",",";","=","+=","-=","*=","/=","%=","&=","^=","|=","<<=",">>="};public static Word left_curly_bracket, right_curly_bracket,left_square_bracket, right_square_bracket,left_bracket, right_bracket,arrow, point, two_add, two_sub,logic_not, logic_and, logic_or,bitwise_not, bitwise_and, bitwise_or, bitwise_xor,add, sub, mul, except, remain,left_move, right_move,less, greater, greater_equal, less_equal,equal, not_equal, question_mark, colon, comma, semicolon,assign, add_assign, sub_assign, mul_assign, except_assign, remain_assign,and_assign, xor_assign, or_assign, left_move_assign, right_move_assign;internal static bool isSemicolo(Word word) {return word .typeNum == semicolon.typeNum;}static Symbols() {Type t = typeof(Symbols);FieldInfo[] fields = t.GetFields();Word word;int index = 0;foreach(FieldInfo f in fields)if(f.FieldType.Equals(typeof(Word))) {word = new Word();word.word = operatorTable[index++];word.typeNum = getTypeNumber(word.word);f.SetValue(t, word);}}public static int getTypeNumber(string s) {int start = 100;for(int i = 0; i < operatorTable.Length; i++) {if(operatorTable[i] == s) {return start + i;}}return WordPicker.noDefine;}internal static bool isArithmeticOperator(Word w) {return w.typeNum == mul.typeNum || w.typeNum == except.typeNum|| w.typeNum == remain.typeNum|| w.typeNum == add.typeNum || w.typeNum == sub.typeNum;}internal static bool isCompareOperator(Word w) {return w.typeNum == less.typeNum || w.typeNum == greater.typeNum ||w.typeNum == less_equal.typeNum || w.typeNum == greater_equal.typeNum ||w.typeNum == equal.typeNum || w.typeNum == not_equal.typeNum;}internal static bool isExpressSymbol(Word w) {return w.typeNum == add.typeNum || w.typeNum == sub.typeNum|| w.typeNum == mul.typeNum || w.typeNum == except.typeNum|| w.typeNum == remain.typeNum || w.typeNum == left_bracket.typeNum || w.typeNum == right_bracket.typeNum|| w.typeNum == WordPicker.identifierTypeNumber|| w.typeNum == WordPicker.numberTypeNumber;}}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace CLanguage {/// <summary>/// 读词缓存流/// </summary>class WordStream {WordPicker wordPicker;List<Word> words = new List<Word>();int index = -1;public WordStream(string file) {wordPicker = new WordPicker(file);}/// <summary>/// 读取下一个词/// </summary>/// <returns></returns>public Word ReadNextWord() {index++;if(words.Count <= index) {Word w = wordPicker.Scanner();if(words.Count == 0 || words[words.Count - 1].typeNum != WordPicker.endTypeNumber)words.Add(w);index = words.Count - 1;}return words[index];}/// <summary>/// 现在的词/// </summary>/// <returns></returns>public Word NowWord() {if(words.Count > index && index >= 0) {return words[index];}return null;}/// <summary>/// 上一个词/// </summary>/// <returns></returns>public Word LastWord() {if(index > 0) {return words[index - 1];}else {return null;}}/// <summary>/// 回退一个词/// </summary>public void retractWord() {if(index >= 0) {index--;}}public void retractWord(int n) {if(index >= 0) {index-=n;}}}
}

输入：

void main(){int first=30;   int second=first*20-5;int three=second*3-20;if(first-second>three){three=23;}
}

输出：

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