Difference between Timestamp - response (5) by nt

hi,
i need to know more about the below code
seconds := (3600 * (To_Number(extract(HOUR FROM diff)))) + (60 * (To_Number(extract (MINUTE FROM diff)))) +(To_Number(extract(SECOND FROM diff)));
I guess TO_NUMBER() does not work in teradata
So how this part of code can be convert into Teradata.
Highly appriciate your quick response.