ast.go
func (node *SubstrExpr) Format(buf *TrackedBuffer) {

	if node.To == nil {
		buf.Myprintf("substr(%v, %v)", node.Name, node.From)
	} else {
		buf.Myprintf("substr(%v, %v, %v)", node.Name, node.From, node.To)
	}
}
func (node *SubstrExpr) Format(buf *TrackedBuffer) {

	if node.To == nil {
		buf.Myprintf("substr(%v, %v)", node.Name, node.From)
	} else {
		buf.Myprintf("substr(%v, %v, %v)", node.Name, node.From, node.To)
	}
}
// Format formats the node.