boolean and if/else

ast/ast.go

@@ -81,6 +81,23 @@ type InfixExpression struct {
 	Right    Expression
 }
 
+type Boolean struct {
+	Token token.Token
+	Value bool
+}
+
+type BlockStatement struct {
+	Token      token.Token // the { token
+	Statements []Statement
+}
+
+type IfExpression struct {
+	Token       token.Token // The 'if' token
+	Condition   Expression
+	Consequence *BlockStatement
+	Alternative *BlockStatement
+}
+
 func (ls *LetStatement) statementNode() {
 }
 func (ls *LetStatement) TokenLiteral() string {
@@ -180,3 +197,45 @@ func (ie *InfixExpression) String() string {
 
 	return out.String()
 }
+
+func (b Boolean) TokenLiteral() string {
+	return b.Token.Literal
+}
+func (b Boolean) String() string {
+	return b.Token.Literal
+}
+func (b Boolean) expressionNode() {}
+
+func (bs BlockStatement) TokenLiteral() string {
+	return bs.Token.Literal
+}
+func (bs BlockStatement) String() string {
+	var out bytes.Buffer
+
+	for _, s := range bs.Statements {
+		out.WriteString(s.String())
+	}
+
+	return out.String()
+}
+func (bs BlockStatement) statementNode() {}
+
+func (ie IfExpression) TokenLiteral() string {
+	return ie.Token.Literal
+}
+func (ie IfExpression) String() string {
+	var out bytes.Buffer
+
+	out.WriteString("if")
+	out.WriteString(ie.Condition.String())
+	out.WriteString(" ")
+	out.WriteString(ie.Consequence.String())
+
+	if ie.Alternative != nil {
+		out.WriteString("else ")
+		out.WriteString(ie.Alternative.String())
+	}
+
+	return out.String()
+}
+func (ie IfExpression) expressionNode() {}