Prefix expressions with bang

madsravn · Nov 1, 2023 · a24d86a · a24d86a
1 parent 4cc2ff6
commit a24d86a
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Showing 4 changed files with 101 additions and 2 deletions.
diff --git a/src/main/java/dk/madsravn/interpreter/evaluator/Evaluator.java b/src/main/java/dk/madsravn/interpreter/evaluator/Evaluator.java
@@ -1,19 +1,37 @@
 package dk.madsravn.interpreter.evaluator;
 
 import dk.madsravn.interpreter.ast.*;
+import dk.madsravn.interpreter.object.BooleanObject;
 import dk.madsravn.interpreter.object.IObject;
 import dk.madsravn.interpreter.object.IntegerObject;
+import dk.madsravn.interpreter.object.NullObject;
 
 import java.util.List;
 
 public class Evaluator {
 
+    private static BooleanObject TRUE = new BooleanObject(true);
+    private static BooleanObject FALSE = new BooleanObject(false);
+    private static NullObject NULL = new NullObject();
+
     public static IObject evaluate(INode node) {
         // TODO: Ugly?
+        if(node instanceof PrefixExpression) {
+            PrefixExpression prefixExpression = (PrefixExpression) node;
+            IObject right = evaluate(prefixExpression.getRight());
+            return evaluatePrefixExpression(prefixExpression.getOperator(), right);
+        }
         if(node instanceof IntegerLiteral) {
-            // TODO: Ugly?
             return new IntegerObject(((IntegerLiteral) node).getValue());
         }
+        if(node instanceof BooleanType) {
+            boolean value =  ((BooleanType)node).getValue();
+            if (value == true) {
+                return TRUE;
+            } else {
+                return FALSE;
+            }
+        }
         if(node instanceof ExpressionStatement) {
             return evaluate(((ExpressionStatement)node).getExpression());
         }
@@ -27,6 +45,31 @@ private static IObject evaluateStatements(List<IStatement> statements) {
         for(IStatement statement : statements) {
             return evaluate(statement);
         }
-        return null;
+        return NULL;
+    }
+
+    private static IObject evaluatePrefixExpression(String operator, IObject right) {
+        if(operator.equals("!")) {
+            return evalulateBangOperatorExpression(right);
+        }
+        return new NullObject();
+    }
+
+    private static IObject evalulateBangOperatorExpression(IObject right) {
+        if (right.equals(TRUE)) {
+            return FALSE;
+        } else if (right.equals(FALSE) || right.equals(NULL)) {
+            return TRUE;
+        }
+        if(right instanceof IntegerObject) {
+            IntegerObject integerObject = (IntegerObject) right;
+            if (integerObject.getValue() == 0) {
+                return TRUE;
+            } else {
+                return FALSE;
+            }
+        }
+        return FALSE;
+
     }
 }
diff --git a/src/main/java/dk/madsravn/interpreter/object/BooleanObject.java b/src/main/java/dk/madsravn/interpreter/object/BooleanObject.java
@@ -3,6 +3,14 @@
 public class BooleanObject implements IObject {
     private boolean value;
 
+    public BooleanObject(boolean value) {
+        this.value = value;
+    }
+
+    public boolean getValue() {
+        return value;
+    }
+
     public String type() {
         return "BOOLEAN";
     }

diff --git a/src/main/java/dk/madsravn/interpreter/repl/Repl.java b/src/main/java/dk/madsravn/interpreter/repl/Repl.java
@@ -1,7 +1,9 @@
 package dk.madsravn.interpreter.repl;
 
 import dk.madsravn.interpreter.ast.Program;
+import dk.madsravn.interpreter.evaluator.Evaluator;
 import dk.madsravn.interpreter.lexer.Lexer;
+import dk.madsravn.interpreter.object.IObject;
 import dk.madsravn.interpreter.parser.Parser;
 import dk.madsravn.interpreter.tokens.Token;
 
@@ -26,6 +28,13 @@ public void start() {
                     continue;
                 }
                 System.out.println(program.string());
+                System.out.println("YIELDS:");
+                IObject evaluated = Evaluator.evaluate(program);
+                if (evaluated != null) {
+                    System.out.println(evaluated.inspect());
+                } else {
+                    System.out.println("NOTHING");
+                }
                 System.out.println("");
             } catch (Exception e) {
 

diff --git a/src/test/java/dk/madsravn/interpreter/evaluator/EvaluatorTest.java b/src/test/java/dk/madsravn/interpreter/evaluator/EvaluatorTest.java
@@ -2,6 +2,7 @@
 
 import dk.madsravn.interpreter.ast.Program;
 import dk.madsravn.interpreter.lexer.Lexer;
+import dk.madsravn.interpreter.object.BooleanObject;
 import dk.madsravn.interpreter.object.IObject;
 import dk.madsravn.interpreter.object.IntegerObject;
 import dk.madsravn.interpreter.parser.Parser;
@@ -17,6 +18,7 @@
 public class EvaluatorTest {
 
     private record EvalIntegerData(String input, int value) { }
+    private record EvalBooleanData(String input, boolean value) { }
 
     @Test
     public void testEvalIntegerExpression() {
@@ -31,12 +33,49 @@ public void testEvalIntegerExpression() {
         }
     }
 
+    @Test
+    public void testBooleanExpression() {
+        List<EvalBooleanData> inputs = Arrays.asList(
+                new EvalBooleanData("true", true),
+                new EvalBooleanData("false", false)
+        );
+
+        for(EvalBooleanData input : inputs) {
+            IObject object = testEval(input.input);
+            testBooleanObject(object, input.value, input.input);
+        }
+    }
+
+    @Test
+    public void testBangOperator() {
+        List<EvalBooleanData> inputs = Arrays.asList(
+                new EvalBooleanData("!true", false),
+                new EvalBooleanData("!false", true),
+                new EvalBooleanData("!5", false),
+                new EvalBooleanData("!!true", true),
+                new EvalBooleanData("!!false", false),
+                new EvalBooleanData("!!5", true),
+                new EvalBooleanData("!!0", false),
+                new EvalBooleanData("!0", true)
+        );
+        for(EvalBooleanData input : inputs) {
+            IObject object = testEval(input.input);
+            testBooleanObject(object, input.value, input.input);
+        }
+    }
+
     private void testIntegerObject(IObject object, int expected) {
         assertTrue(object instanceof IntegerObject);
         IntegerObject integerObject = (IntegerObject) object;
         assertEquals(integerObject.getValue(), expected);
     }
 
+    private void testBooleanObject(IObject object, boolean expected, String input) {
+        assertTrue(object instanceof BooleanObject);
+        BooleanObject booleanObject = (BooleanObject) object;
+        assertEquals(booleanObject.getValue(), expected, input);
+    }
+
     private IObject testEval(String input) {
         Lexer lexer = new Lexer(input);
         Parser parser = new Parser(lexer);