想了解更多内容，移步至编译原理专栏
在上次实验的基础上进行改进，能够识别多个错误，本文的只进行了部分数据的测试，所以可能会有其他错误识别不出来
部分缺失的代码请参考我之前写的博客，可以查看完整的代码
本博客的程序只能识别赋值语句，能够输出并输出多种错误的类型，并且实现了错误定位功能
package codescanner; import java.util.ArrayList; public class IrParser { private Analyzer analyzer; private ArrayList<Word> list = new ArrayList<>(); private Word word; private int index = 0; // 从列表中获取单词的下标 private boolean error = false; //标记是否检测到错误 public int rowNum = 1; //用来记录行数 public IrParser() { analyzer = new Analyzer("input.txt", "output.txt"); analyzer.analyze(analyzer.getContent()); list = analyzer.getList(); } public void parse() { if(list.size() > 0 && (word = getNext(list)).getTypenum() !=1) { error = true; index--; System.out.print("begin错误"); System.out.println(" 识别符号为 " + word.getWord() + " " + "位置: " + rowNum + "行"); } //分隔符 pretreatment(); if(list.size() > 0) { word = getNext(list); if (word == null) { error = true; System.out.print("缺end错误"); System.out.println(" 文件已结束 " + "位置: " + rowNum + "行"); }else if(word.getTypenum() != 6){ error = true; System.out.print("缺end错误"); System.out.println(" 识别符号为 " + word.getWord() + " " + "位置: " + rowNum + "行"); } } if (!error) { System.out.println("success"); } } /** * 预处理 */ public void pretreatment() { while (word != null && word.getTypenum() != 6) { statement(); } index--; } /** * 赋值错误和语句错误 */ public void statement() { word = getNext(list); if (word != null && word.getTypenum() != 26) { if (word.getTypenum() == 10) { assignment(); } else { if (word.getTypenum() != 0 && word.getTypenum() != 6) { error = true; System.out.print("语句错误"); System.out.println(" 识别符号为 " + word.getWord() + " " + "位置: " + rowNum + "行"); assignment(); } } } } /** * 赋值号错误 */ public void assignment() { word = getNext(list); if (word != null ) { if (word.getTypenum() == 18) { expression(); } else { error = true; System.out.print("赋值号错误"); System.out.println(" 识别符号为 " + word.getWord() + " " + "位置: " + + rowNum + "行"); expression(); } } } /** * 分析表达式表达式 */ public void expression() { if (word.getTypenum() == 26) return; word = getNext(list); if (word != null) { term(); while (word.getTypenum() == 13 || word.getTypenum() == 14) { word = getNext(list); term(); } } } public void term() { if (word != null) { factor(); while (word.getTypenum() == 15 || word.getTypenum() == 16) { word = getNext(list); factor(); } } } /** * "("错误 和 表达式错误 */ public void factor() { if (word != null) { if (word.getTypenum() == 10 || word.getTypenum() == 11) { word = getNext(list); } else if (word.getTypenum() == 27) { expression(); if (word.getTypenum() == 28) { word = getNext(list); } else { error = true; System.out.print("')'错误"); System.out.println(" 识别符号为 " + word.getWord() + " " + "位置: " + rowNum + "行"); if (word.getTypenum() == 26) return; word = getNext(list); } } else { error = true; System.out.print("表达式错误"); System.out.println(" 识别符号为 " + word.getWord() + " " + "位置: " + rowNum + "行"); if (word.getTypenum() == 26) return; word = getNext(list); } } } /** * 取下一个词，如果是读取到换行，就增加行数， * @param list * @return */ public Word getNext(ArrayList<Word> list) { if (index < list.size()) { Word currentWord = list.get(index++); while (currentWord.getTypenum() == 30 || currentWord.getTypenum() == 31) { //因为一个换行字符被我转换成长度为2字符串了，所以要除以2 rowNum += currentWord.getWord().length()/2; currentWord = list.get(index++); } return currentWord; } else { return null; } } public int getIndex() { return index; } public void setIndex(int index) { this.index = index; } public static void main(String[] args) { IrParser parser = new IrParser(); parser.parse(); } }实验数据
//正确测试例子 //begin a:=9; x:=2*3; b:=a+x end # //缺begin错误 x:=a+b*c; //表达式错误 a:=2+; x:=2*3; b:=a+x; //赋值符号错误 a=9; x:=2*3; b:=a+x; //')'错误 和 表达式错误 a:=9; x:=2*3; b:=(a+; //语句错误 //if a>0 then a:=1; if :=1; //表达式错误 x:=4+; //缺end错误 x:=a+b*c; #以上的数据应该在当前项目目录下新建一个文件“input.txt”， 并且以“#”作为文件结束符
