First commit with Eval

src/main/java/dk/madsravn/interpreter/evaluator/Evaluator.java

@@ -0,0 +1,32 @@
+package dk.madsravn.interpreter.evaluator;
+
+import dk.madsravn.interpreter.ast.*;
+import dk.madsravn.interpreter.object.IObject;
+import dk.madsravn.interpreter.object.IntegerObject;
+
+import java.util.List;
+
+public class Evaluator {
+
+    public static IObject evaluate(INode node) {
+        // TODO: Ugly?
+        if(node instanceof IntegerLiteral) {
+            // TODO: Ugly?
+            return new IntegerObject(((IntegerLiteral) node).getValue());
+        }
+        if(node instanceof ExpressionStatement) {
+            return evaluate(((ExpressionStatement)node).getExpression());
+        }
+        if(node instanceof Program) {
+            return evaluateStatements(((Program)node).getStatements());
+        }
+        return null;
+    }
+
+    private static IObject evaluateStatements(List<IStatement> statements) {
+        for(IStatement statement : statements) {
+            return evaluate(statement);
+        }
+        return null;
+    }
+}

src/main/java/dk/madsravn/interpreter/object/BooleanObject.java

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+package dk.madsravn.interpreter.object;
+
+public class BooleanObject implements IObject {
+    private boolean value;
+
+    public String type() {
+        return "BOOLEAN";
+    }
+
+    public String inspect() {
+        return "" + value;
+    }
+}
+

src/main/java/dk/madsravn/interpreter/object/IObject.java

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+package dk.madsravn.interpreter.object;
+
+public interface IObject {
+    String type();
+    String inspect();
+
+}

src/main/java/dk/madsravn/interpreter/object/IntegerObject.java

@@ -0,0 +1,25 @@
+package dk.madsravn.interpreter.object;
+
+public class IntegerObject implements IObject {
+    private int value;
+
+    public IntegerObject(int value) {
+        this.value = value;
+    }
+
+    public int getValue() {
+        return value;
+    }
+
+    @Override
+    public String inspect() {
+        return "" + value;
+    }
+
+    // TODO: Create enum for this.
+    @Override
+    public String type() {
+        return "INTEGER";
+    }
+
+}

src/main/java/dk/madsravn/interpreter/object/NullObject.java

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+package dk.madsravn.interpreter.object;
+
+public class NullObject implements IObject {
+    @Override
+    public String type() {
+        return "NULL";
+    }
+
+    @Override
+    public String inspect() {
+        return "null";
+    }
+
+}

src/test/java/dk/madsravn/interpreter/evaluator/EvaluatorTest.java

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+package dk.madsravn.interpreter.evaluator;
+
+import dk.madsravn.interpreter.ast.Program;
+import dk.madsravn.interpreter.lexer.Lexer;
+import dk.madsravn.interpreter.object.IObject;
+import dk.madsravn.interpreter.object.IntegerObject;
+import dk.madsravn.interpreter.parser.Parser;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static dk.madsravn.interpreter.evaluator.Evaluator.evaluate;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class EvaluatorTest {
+
+    //TODO: Use record instead. Then we get all of this
+    private class EvalIntegerData {
+        public String input;
+        public int value;
+        public EvalIntegerData(String input, int value) {
+            this.input = input;
+            this.value = value;
+        }
+    }
+
+    @Test
+    public void testEvalIntegerExpression() {
+        List<EvalIntegerData> inputs = Arrays.asList(
+                new EvalIntegerData("5", 5),
+                new EvalIntegerData("10", 10)
+        );
+
+        for(EvalIntegerData input : inputs) {
+            IObject object = testEval(input.input);
+            testIntegerObject(object, input.value);
+        }
+    }
+
+    private void testIntegerObject(IObject object, int expected) {
+        assertTrue(object instanceof IntegerObject);
+        IntegerObject integerObject = (IntegerObject) object;
+        assertEquals(integerObject.getValue(), expected);
+    }
+
+    private IObject testEval(String input) {
+        Lexer lexer = new Lexer(input);
+        Parser parser = new Parser(lexer);
+        Program program = parser.parseProgram();
+
+        return evaluate(program);
+    }
+}