识别分界符

vincentbel · Jan 10, 2015 · a74684f · a74684f
1 parent 7d2cb7d
commit a74684f
Showing 1 changed file with 64 additions and 2 deletions.
diff --git a/src/com/vincentbel/compiler/LexicalAnalyzer.java b/src/com/vincentbel/compiler/LexicalAnalyzer.java
@@ -20,6 +20,11 @@ public class LexicalAnalyzer {
     private int currentLineStringLength = 0;  // 当前读取的一行源代码的的长度
     private int currentLineStringIndex = 0;  // 读取到的某个具体字符下标
 
+    // 简单的操作符，读取到一个字符后就能确定类型的字符
+    // 也就是 . , ; = + - ( ) * /
+    private int[] simpleOperators;
+
+
     /**
      * Constructor
      *
@@ -32,6 +37,20 @@ public LexicalAnalyzer(String filePath) {
             e.printStackTrace();
             System.out.println("错误！ 文件不存在");
         }
+
+        // 初始化简单操作符
+        simpleOperators = new int[256]; // 因为char的范围是[0, 255]，所以数组大小最大只需256
+        Arrays.fill(simpleOperators, Symbol.NUL); // 对于其他不可识别的字符，全都设置为[NULL]
+        simpleOperators['.'] = Symbol.PERIOD;
+        simpleOperators[','] = Symbol.COMMA;
+        simpleOperators[';'] = Symbol.SEMICOLON;
+        simpleOperators['='] = Symbol.EQUAL;
+        simpleOperators['+'] = Symbol.PLUS;
+        simpleOperators['-'] = Symbol.MINUS;
+        simpleOperators['('] = Symbol.LEFT_PARENTHESIS;
+        simpleOperators[')'] = Symbol.RIGHT_PARENTHESIS;
+        simpleOperators['*'] = Symbol.MULTIPLY;
+        simpleOperators['/'] = Symbol.DIVIDE;
     }
 
     /**
@@ -183,9 +202,52 @@ private Symbol getNumber() {
      * @return Symbol
      */
     private Symbol getOperator() {
+        Symbol symbol;
 
-        Symbol symbol = null;
-        // TODO 实现
+        switch (currentChar) {
+            case ':':
+                getChar();
+                if (currentChar == '=') { // 赋值符号 :=
+                    symbol = new Symbol(Symbol.BECOMES);
+                    getChar();
+                } else {
+                    // ERROR，设置symbol为null
+                    symbol = new Symbol(Symbol.NUL);
+                }
+                break;
+            case '<':
+                getChar();
+                switch (currentChar) {
+                    case '>':  // 不等于 <>
+                        symbol = new Symbol(Symbol.NOT_EQUAL);
+                        getChar();
+                        break;
+                    case '=':  // 小于等于 <=
+                        symbol = new Symbol(Symbol.LESS_OR_EQUAL);
+                        getChar();
+                        break;
+                    default: // 小于
+                        symbol = new Symbol(Symbol.LESS);
+                        break;
+                }
+                break;
+            case '>':
+                getChar();
+                if (currentChar == '=') { // 大于等于 >=
+                    symbol = new Symbol(Symbol.GREATER_OR_EQUAL);
+                    getChar();
+                } else { // 大于
+                    symbol = new Symbol(Symbol.GREATER);
+                }
+                break;
+            default:
+                // 直接利用simpleOperators[]数组填充即可
+                symbol = new Symbol(simpleOperators[currentChar]);
+
+                // 提前读取下一个字符
+                getChar();
+                break;
+        }
 
         return symbol;
     }