boolean object evaluator

evaluator/evaluator.go

@@ -5,6 +5,12 @@ import (
 	"github/runnignwater/monkey/object"
 )
 
+var (
+	NULL  = &object.Null{}
+	TRUE  = &object.Boolean{Value: true}
+	FALSE = &object.Boolean{Value: false}
+)
+
 func Eval(node ast.Node) object.Object {
 	switch node := node.(type) {
 	// Statements
@@ -17,6 +23,8 @@ func Eval(node ast.Node) object.Object {
 	// Expression
 	case *ast.IntegerLiteral:
 		return &object.Integer{Value: node.Value}
+	case *ast.Boolean:
+		return nativeBooleanObject(node.Value)
 	}
 
 	return nil
@@ -30,3 +38,11 @@ func evalStatements(stmts []ast.Statement) object.Object {
 	}
 	return result
 }
+
+func nativeBooleanObject(input bool) *object.Boolean {
+	if input {
+		return TRUE
+	} else {
+		return FALSE
+	}
+}

evaluator/evaluator_test.go

@@ -22,6 +22,21 @@ func TestEvalIntegerExpression(t *testing.T) {
 	}
 }
 
+func TestEvalBooleanExpression(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected bool
+	}{
+		{"true", true},
+		{"false", false},
+	}
+
+	for _, tt := range tests {
+		evaluated := testEval(tt.input)
+		testBooleanObject(t, evaluated, tt.expected)
+	}
+}
+
 func testIntegerObject(t *testing.T, obj object.Object, expected int64) bool {
 	result, ok := obj.(*object.Integer)
 	if !ok {
@@ -34,7 +49,18 @@ func testIntegerObject(t *testing.T, obj object.Object, expected int64) bool {
 	}
 	return true
 }
-
+func testBooleanObject(t *testing.T, obj object.Object, expected bool) bool {
+	result, ok := obj.(*object.Boolean)
+	if !ok {
+		t.Errorf("object is not Boolean. got=%T (%+v)", obj, obj)
+		return false
+	}
+	if result.Value != expected {
+		t.Errorf("object has wrong value. got=%t, want=%t", result.Value, expected)
+		return false
+	}
+	return true
+}
 func testEval(input string) object.Object {
 	l := lexer.New(input)
 	p := parser.New(l)

repl/repl.go

@@ -3,6 +3,7 @@ package repl
 import (
 	"bufio"
 	"fmt"
+	"github/runnignwater/monkey/evaluator"
 	"github/runnignwater/monkey/lexer"
 	"github/runnignwater/monkey/parser"
 	"io"
@@ -37,11 +38,14 @@ func Start(in io.Reader, out io.Writer) {
 			continue
 		}
 
-		if _, err := io.WriteString(out, program.String()); err != nil {
-			log.Fatal(err)
-		}
-		if _, err := io.WriteString(out, "\n"); err != nil {
-			log.Fatal(err)
+		evaluated := evaluator.Eval(program)
+		if evaluated != nil {
+			if _, err := io.WriteString(out, evaluated.Inspect()); err != nil {
+				panic(err)
+			}
+			if _, err := io.WriteString(out, "\n"); err != nil {
+				panic(err)
+			}
 		}
 	}
 }