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LA.h

@@ -0,0 +1,232 @@
+#include<iostream>
+#include<fstream>
+#include<cstdlib> 
+#include<string>
+using namespace std;
+int row, column;
+const string keyword[15] = { "program", "const", "var", "procedure", "begin", "if", "end", "while", "call", "read", "write", "then", "odd", "do" ,"else" };
+fstream infile;
+fstream outfile;
+/*void GetChar()
+{
+	if(GetBC())
+	{
+		while(GetBC()) infile>>ch;
+	}
+}*/
+/*   whether it is blank   */
+bool GetBC(char ch)
+{
+	if (ch == '\n' || ch == '\r')
+	{
+		row++;
+		column = 1;
+		return true;
+	}
+	else if (ch == '\t')
+	{
+		column += 4;
+		return true;
+	}
+	else if (ch == ' ')
+	{
+		column++;
+		return true;
+	}
+	else return false;
+}
+string Concat(string strToken, char ch)
+{
+	return strToken + ch;
+}
+/*   whether it is a letter   */
+bool IsLetter(char ch)
+{
+	if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')) return true;
+	else return false;
+}
+/*   whether it is a number   */
+bool IsDigit(char ch)
+{
+	if (ch >= '0' && ch <= '9') return true;
+	else return false;
+}
+/*   whether it is a keyword   */
+int Reserve(string strToken)
+{
+	for (int i = 0; i < 15; i++)
+	{
+		if (strToken.compare(keyword[i]) == 0) return i + 1;
+	}
+	return 0;
+}
+/*   back one letter   */
+void Retract()//回调一个字符位置 
+{
+	if (!infile.eof())
+	{
+		infile.seekg(-1, ios::cur);
+	}
+}
+int LA()
+{
+	infile.open("test2.txt");//open file "test1.txt"
+	if (!infile)
+	{
+		cout << "Can't open test1.txt" << "\n";
+		exit(0);
+	}
+	outfile.open("res1.txt");
+	if (!outfile)
+	{
+		cout << "Can't open res1.txt" << "\n";
+		exit(1);
+	}
+	row = 1;
+	column = 1;//row and column initialization
+
+	string strToken = "";
+	char ch;
+
+	while (!infile.eof())
+	{
+		/*   12 cases   */
+		ch = infile.get();
+		if (GetBC(ch)) strToken = "";//case 1:blank; circle until it is non-blank
+		else if (IsLetter(ch))//case 2:word;keyword or id
+		{
+			strToken = Concat(strToken, ch);
+			column++;
+			ch = infile.get();
+			while (IsLetter(ch) || IsDigit(ch))
+			{
+				column++;
+				strToken = Concat(strToken, ch);
+				ch = infile.get();
+			}
+			if (Reserve(strToken))//关键字 
+			{
+				outfile << strToken << "\t" << "keyword" << "\t" << row << "\t" << column << endl;
+			}
+			else
+			{
+				outfile << strToken << "\t" << "id" << "\t" << row << "\t" << column << endl;
+			}
+			//cout << strToken << "\n";
+			strToken = "";
+			Retract();  //返回上一位 
+			//outfile << ch << "\n";
+		}
+		else if (IsDigit(ch))//case 3:number
+		{
+			strToken = Concat(strToken, ch);
+			column++;
+			ch = infile.get();
+			while (IsDigit(ch))
+			{
+				column++;
+				strToken = Concat(strToken, ch);
+				ch = infile.get();
+			}
+			if (IsLetter(ch))
+			{				
+				while (IsLetter(ch) || IsDigit(ch))
+				{
+					strToken = Concat(strToken, ch);
+					column++;
+					ch = infile.get();
+				}
+				cout << "[Lexcial ERROR]"<<strToken << "\t" << "[" << row << "," << column << "]" << "\t" << "Invalid id:\n";
+				outfile << strToken << "\t" << "id" << "\t" << row << "\t" << column << endl;
+			}
+			else outfile << strToken << "\t" << "int" << "\t" << row << "\t" << column << endl;
+			strToken = "";
+			Retract();
+		}
+		else if (ch == '<')//case 4:<; next is '>' or '=' or ""
+		{
+			column++;
+			ch = infile.get();
+			if (ch == '>')
+			{
+				column++;
+				outfile << "<>" << "\t" << "lop" << "\t" << row << "\t" << column << endl;
+			}
+			else if (ch == '=')
+			{
+				column++;
+				outfile << "<=" << "\t" << "lop" << "\t" << row << "\t" << column << endl;
+			}
+			else
+			{
+				outfile << "<" << "\t" << "lop" << "\t" << row << "\t" << column << endl;
+				Retract();
+			}
+		}
+		else if (ch == '>')//case 5:>;next is '=' or ""
+		{
+			column++;
+			ch = infile.get();
+			if (ch == '=')
+			{
+				column++;
+				outfile << ">=" << "\t" << "lop" << "\t" << row << "\t" << column << endl;
+			}
+			else
+			{
+				outfile << ">" << "\t" << "lop" << "\t" << row << "\t" << column << endl;
+				Retract();
+			}
+		}
+		else if (ch == ':')//case 6:next must be '='
+		{
+			column++;
+			ch = infile.get();
+			if (ch == '=')
+			{
+				column++;
+				outfile << ":=" << "\t" << "..." << "\t" << row << "\t" << column << endl;
+			}
+			else
+			{
+				cout << "[Lexcial ERROR]" << "[" << row << "," << column << "] " << "Missing \"=\" near the \":\" " << endl;
+				outfile << ":=" << "\t" << "..." << "\t" << row << "\t" << column << endl;
+				Retract();
+			}
+		}
+		else if (ch == '=')//case 7:'='
+		{
+			column++;
+			outfile << ch << "\t" << "lop" << "\t" << row << "\t" << column << endl;
+		}
+		else if (ch == '+' || ch == '-')//case 8:'+' or '-';
+		{
+			column++;
+			outfile << ch << "\t" << "aop" << "\t" << row << "\t" << column << endl;
+		}
+		else if (ch == '*' || ch == '/')//case 9:'*' or '/';
+		{
+			column++;
+			outfile << ch << "\t" << "mop" << "\t" << row << "\t" << column << endl;
+		}
+		else if (ch == ';')//case 10:';'
+		{
+			column++;
+			outfile << ch << "\t" << "..." << "\t" << row << "\t" << column << endl;
+		}
+		else if (ch == '(' || ch == ')' || ch == ',')//case 11:'(' or ')' or ',';
+		{
+			column++;
+			outfile << ch << "\t" << "..." << "\t" << row << "\t" << column << endl;
+		}
+		else//case 12:else
+		{
+			column++;
+			outfile << ch << "\t" << "UNKOWEN" << "\t" << row << "\t" << column << endl;
+		}
+	}
+	infile.close();//close file "test1.txt"
+	outfile.close();
+	//cout << "succeefully!" << endl;
+	return 0;
+}