Expression Evaluator Skeleton

Author: Eble

src/main/java/com/ExpressionEvaluatorMain.java

@@ -0,0 +1,12 @@
+package com;
+
+public class ExpressionEvaluatorMain {
+
+    public static void main(String[] args) throws Exception {
+        com.compiler.Lexer lexer = new com.compiler.Lexer();
+        com.compiler.ExpressionEvaluator evaluator = new com.compiler.ExpressionEvaluator(lexer);
+        int result = evaluator.eval("4+5");
+        System.out.println(result);
+    }
+
+}

src/main/java/com/ParserExample.java src/main/java/com/ParserExampleMain.javasrc/main/java/com/ParserExample.java renamed to src/main/java/com/ParserExampleMain.java

@@ -1,7 +1,7 @@
 package com;
 
 
-public class ParserExample {
+public class ParserExampleMain {
     com.compiler.Lexer m_lexer;
 
     void parsePrint() throws Exception {
@@ -26,7 +26,7 @@ void parse(String input) throws Exception {
     }
 
     public static void main(String[] args) throws Exception {
-        ParserExample parser = new ParserExample();
+        ParserExampleMain parser = new ParserExampleMain();
         parser.parse("""
                 PRINT 1;
                 PRINT 2;

src/main/java/com/compiler/ExpressionEvaluator.java

@@ -0,0 +1,58 @@
+package com.compiler;
+
+public class ExpressionEvaluator implements ExpressionEvaluatorIntf {
+    private Lexer m_lexer;
+
+    public ExpressionEvaluator(Lexer lexer) {
+        m_lexer = lexer;
+    }
+
+    @Override
+    public int eval(String val) throws Exception {
+        m_lexer.init(val);
+        return getQuestionMarkExpr();
+    }
+
+    int getParantheseExpr() throws Exception {
+        Token curToken = m_lexer.lookAhead();
+        m_lexer.expect(Token.Type.INTEGER);
+        return Integer.valueOf(curToken.m_value);
+    }
+
+    int getDashExpr() throws Exception {
+        return getParantheseExpr();
+    }
+    
+    int getUnaryExpr() throws Exception {
+        return getDashExpr();
+    }
+
+    int getMulDivExpr() throws Exception {
+        return getUnaryExpr();
+    }
+
+    int getPlusMinusExpr() throws Exception {
+        int result = getMulDivExpr();
+        return result;
+    }
+
+    int getBitAndOrExpr() throws Exception {
+        return getPlusMinusExpr();
+    }
+
+    int getShiftExpr() throws Exception {
+        return getBitAndOrExpr();
+    }
+
+    int getCompareExpr() throws Exception {
+        return getShiftExpr();
+    }
+
+    int getAndOrExpr() throws Exception {
+        return getCompareExpr();
+    }
+
+    int getQuestionMarkExpr() throws Exception {
+        return getAndOrExpr();
+    }
+}

src/main/java/com/compiler/ExpressionEvaluatorIntf.java

@@ -0,0 +1,10 @@
+package com.compiler;
+
+public interface ExpressionEvaluatorIntf {
+    
+    /**
+     * evaluates the expression val and returns result as integer
+     */
+    int eval(String val) throws Exception;
+
+}

src/test/java/com/compiler/TestExpressionEvaluatorBase.java

@@ -0,0 +1,11 @@
+package com.compiler;
+
+public class TestExpressionEvaluatorBase {
+
+    public int evalExpression(String input) throws Exception {
+        Lexer lexer = new Lexer();
+        ExpressionEvaluatorIntf evaluator = new ExpressionEvaluator(lexer);
+        int result = evaluator.eval(input);
+        return result;
+    }
+}

src/test/java/com/compiler/TestPlusMinusExpr.java

@@ -0,0 +1,14 @@
+package com.compiler;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class TestPlusMinusExpr extends TestExpressionEvaluatorBase {
+
+    @Test
+    public void testPlusMinusExpr() throws Exception {
+      assertEquals(5, evalExpression("5"));
+    }
+
+}