feat: add String() method to all statements

golang-tools/interpreters/monkey-lang/ast/ast.go

@@ -1,9 +1,13 @@
 package ast
 
-import "vighnesh153/interpreters/monkey-lang/token"
+import (
+	"bytes"
+	"vighnesh153/interpreters/monkey-lang/token"
+)
 
 type Node interface {
 	TokenLiteral() string
+	String() string
 }
 
 type Statement interface {
@@ -20,6 +24,16 @@ type Program struct {
 	Statements []Statement
 }
 
+func (p *Program) String() string {
+	var out bytes.Buffer
+
+	for _, s := range p.Statements {
+		out.WriteString(s.String())
+	}
+
+	return out.String()
+}
+
 func (p *Program) TokenLiteral() string {
 	if len(p.Statements) > 0 {
 		return p.Statements[0].TokenLiteral()
@@ -36,6 +50,21 @@ type LetStatement struct {
 
 func (ls *LetStatement) statementNode()       {}
 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()
+}
 
 type Identifier struct {
 	Token token.Token // token.IDENTIFIER token
@@ -44,11 +73,39 @@ type Identifier struct {
 
 func (i *Identifier) expressionNode()      {}
 func (i *Identifier) TokenLiteral() string { return i.Token.Literal }
+func (i *Identifier) String() string       { return i.Value }
 
 type ReturnStatement struct {
 	Token       token.Token // the token.RETURN token
 	ReturnValue Expression
 }
 
-func (ls *ReturnStatement) statementNode()       {}
-func (ls *ReturnStatement) TokenLiteral() string { return ls.Token.Literal }
+func (rs *ReturnStatement) statementNode()       {}
+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()
+}
+
+type ExpressionStatement struct {
+	Token      token.Token // the first token of the expression
+	Expression Expression
+}
+
+func (es *ExpressionStatement) statementNode()       {}
+func (es *ExpressionStatement) TokenLiteral() string { return es.Token.Literal }
+func (es *ExpressionStatement) String() string {
+	if es.Expression != nil {
+		return es.Expression.String()
+	}
+	return ""
+}

golang-tools/interpreters/monkey-lang/ast/ast_test.go

@@ -0,0 +1,37 @@
+package ast
+
+import (
+	"testing"
+	"vighnesh153/interpreters/monkey-lang/token"
+)
+
+func TestAstString(t *testing.T) {
+	program := &Program{
+		Statements: []Statement{
+			&LetStatement{
+				Token: token.Token{
+					Type:    token.LET,
+					Literal: "let",
+				},
+				Name: &Identifier{
+					Token: token.Token{
+						Type:    token.IDENTIFIER,
+						Literal: "pikachu",
+					},
+					Value: "pikachu",
+				},
+				Value: &Identifier{
+					Token: token.Token{
+						Type:    token.IDENTIFIER,
+						Literal: "best",
+					},
+					Value: "best",
+				},
+			},
+		},
+	}
+
+	if program.String() != "let pikachu = best;" {
+		t.Errorf("program.String() wrong. got=%q", program.String())
+	}
+}