Added Evaulator and Object Model

2 files changed, 78 insertions, 0 deletions

diff --git a/evaluator/evaluator.go b/evaluator/evaluator.go
new file mode 100644
index 0000000..8d1b26d
--- /dev/null
+++ b/evaluator/evaluator.go
@@ -0,0 +1,34 @@
+package evaluator
+
+import (
+	"mana/ast"
+	"mana/object"
+)
+
+// Eval evaluates the given ast.Node and returns an object.Object.
+func Eval(node ast.Node) object.Object {
+	switch node := node.(type) {
+	// Statements
+	case *ast.Program:
+		return evalStatements(node.Statements)
+
+	case *ast.ExpressionStatement:
+		return Eval(node.Expression)
+
+	// Expressions
+	case *ast.IntegerLiteral:
+		return &object.Integer{Value: node.Value}
+	}
+
+	return nil
+}
+
+func evalStatements(stmts []ast.Statement) object.Object {
+	var result object.Object
+
+	for _, statement := range stmts {
+		result = Eval(statement)
+	}
+
+	return result
+}
diff --git a/evaluator/evaluator_test.go b/evaluator/evaluator_test.go
new file mode 100644
index 0000000..cd1edb1
--- /dev/null
+++ b/evaluator/evaluator_test.go
@@ -0,0 +1,44 @@
+package evaluator
+
+import (
+	"mana/lexer"
+	"mana/object"
+	"mana/parser"
+
+	"testing"
+)
+
+func TestEvalIntegerExpression(t *testing.T) {
+	tests := []struct {
+		input	string
+		expected int64
+	}{
+		{"5", 5},
+		{"10", 10},
+	}
+
+	for _, tt := range tests {
+		evalated := testEval(tt.input)
+		testIntegerObject(t, evalated, tt.expected)
+	}
+}
+
+func testEval(input string) object.Object {
+	l := lexer.New(input)
+	p := parser.New(l)
+	program := p.ParseProgram()
+	return Eval(program)
+}
+
+func testIntegerObject(t *testing.T, obj object.Object, expected int64) bool {
+	result, ok := obj.(*object.Integer)
+	if !ok {
+		t.Errorf("object is not Integer. got=%T (%+v)", obj, obj)
+		return false
+	}
+	if result.Value != expected {
+		t.Errorf("object has wrong value. got=%d, want=%d", result.Value, expected)
+		return false
+	}
+	return true
+}