diff --git a/ast/ast.go b/ast/ast.go
index 612849f..881ffde 100644
--- a/ast/ast.go
+++ b/ast/ast.go
@@ -1,9 +1,13 @@
 package ast
 
-import "monkey/token"
+import (
+	"bytes"
+	"monkey/token"
+)
 
 type Node interface {
 	TokenLiteral() string
+	String() string
 }
 
 type Statement interface {
@@ -16,6 +20,14 @@ type Expression interface {
 	expression_node()
 }
 
+func (l_program *Program) String() string {
+	var out bytes.Buffer
+	for _, s := range l_program.Statements {
+		out.WriteString(s.String())
+	}
+	return out.String()
+}
+
 type Program struct {
 	Statements []Statement
 }
@@ -36,18 +48,43 @@ type ReturnStatement struct {
 	ReturnValue Expression
 }
 
+type ExpressionStatement struct {
+	Token      token.Token // the first token in the expression
+	Expression Expression
+}
+
+// Let Statements
 func (ls *LetStatement) statement_node() {}
 
 func (ls *LetStatement) TokenLiteral() string {
 	return ls.Token.Literal
 }
 
+func (ls *LetStatement) String() string {
+	var out bytes.Buffer
+	out.WriteString(ls.TokenLiteral() + " ")
+	out.WriteString(ls.Name.String())
+	out.WriteString(" = ")
+
+	if ls.Value != nil {
+		out.WriteString(ls.Value.String())
+	}
+	out.WriteString(";")
+	return out.String()
+}
+
+// Identifier
 func (i *Identifier) expression_node() {}
 
 func (i *Identifier) TokenLiteral() string {
 	return i.Token.Literal
 }
 
+func (i *Identifier) String() string {
+	return i.Value
+}
+
+// Program
 func (p *Program) TokenLiteral() string {
 	if len(p.Statements) > 0 {
 		return p.Statements[0].TokenLiteral()
@@ -56,8 +93,33 @@ func (p *Program) TokenLiteral() string {
 	}
 }
 
+// Return Statements
 func (rs *ReturnStatement) statement_node() {}
 
 func (rs *ReturnStatement) TokenLiteral() string {
 	return rs.Token.Literal
 }
+
+func (rs *ReturnStatement) String() string {
+	var out bytes.Buffer
+	out.WriteString(rs.TokenLiteral() + " ")
+	if rs.ReturnValue != nil {
+		out.WriteString(rs.ReturnValue.String())
+	}
+	out.WriteString(";")
+	return out.String()
+}
+
+// Expression Statement
+func (es *ExpressionStatement) statement_node() {}
+
+func (es *ExpressionStatement) TokenLiteral() string {
+	return es.Token.Literal
+}
+
+func (es *ExpressionStatement) String() string {
+	if es.Expression != nil {
+		return es.Expression.String()
+	}
+	return ""
+}
diff --git a/ast/ast_test.go b/ast/ast_test.go
new file mode 100644
index 0000000..7d2addd
--- /dev/null
+++ b/ast/ast_test.go
@@ -0,0 +1,28 @@
+package ast
+
+import (
+	"monkey/token"
+	"testing"
+)
+
+func TestString(l_test *testing.T) {
+	program := &Program{
+		Statements: []Statement{
+			&LetStatement{
+				Token: token.Token{Type: token.LET, Literal: "let"},
+				Name: &Identifier{
+					Token: token.Token{Type: token.IDENT, Literal: "my_var"},
+					Value: "my_var",
+				},
+				Value: &Identifier{
+					Token: token.Token{Type: token.IDENT, Literal: "another_var"},
+					Value: "another_var",
+				},
+			},
+		},
+	}
+
+	if program.String() != "let my_var = another_var;" {
+		l_test.Errorf("program.String() wrong, got=%q", program.String())
+	}
+}
diff --git a/main.go b/main.go
index 53a02aa..bf97f45 100644
--- a/main.go
+++ b/main.go
@@ -1,10 +1,9 @@
 /* TODO(tijani):
- 
- - add quit command to the repl.
- - remove semicolons from the language to mark the end of a statement.
- - add line and position reporting in the lexer when a lexing or parsing error occurs.
-*/
 
+- add quit command to the repl.
+- remove semicolons from the language to mark the end of a statement.
+- add line and position reporting in the lexer when a lexing or parsing error occurs.
+*/
 
 package main