XPath function similar to Decode in database

Question

Hello All,
I was wondering if there is an XPATH Function equivalent to DECODE Keyword in Database.
I will give an example of what i want. I have a package which accepts a set of inputs, in the DB adapter call while assigning inputs, if the client input is Null i want to assign 'xyz' to one of the parameters and if its not null i want to concat input with '123' and assign it to a parameter. (This is not an original requirement, the intent is instead of using a set of switch statements can we do it in one assign)
Thanks
Krishna

Answer 1

You can use something like this :
concat(
substring($s1, 1, number($condition) * string-length($s1)),
substring($s2, 1, number(not($condition)) * string-length($s2))
So, you will get output as "s1" or "s2" depending upon the condition.
Hope it helps.