Unavailable string functions?

[ATroyer]

It appears that some of the string functions in the standard library are unavailable?

I am using INDE 21.5, with an app using only SQL Server databases, with compatibility to other databases turned off.
I try to assign the "Difference" function to an integer variable and it does not appear as an option in the drop-down list. The same occurs when using the "Sounds Like" function with a boolean variable. On the other hand, the "Length" function, which returns an int, works fine.

What am I missing?