How to get a substring in a Workflow Activity?

Question

I'm concatenating some values into a Summary field in a workflow activity as follows:
IIF(Eq([//Target/Code1],True),"1,","")+IIF(Eq([//Target/Code2],True),"2,","")+IIF(Eq([//Target/Code3],True),"3,","")
So if Code1 and Code2 are true I get a Summary Value of 1,2,
Now I want to trim the trailing comma.
So I did this
Left([//Target/Summary],Add(Length([//Target/Summary]),-1))
This part doesn't work.  It says Left is improperly formatted or missing a parameter.
If I put a numeric value like 1 or 2 as the second value it works.
 Any suggestions on how to get trim a character off the end of a string in a FIM Workflow activity?

Answer 1

Length isn't a function supported by the FIM Function evaluator Workflow activity. (Which is frustrating).
Here is my sloppy approach using the built-in tool (lots of nesting so if you need to do this for more than 3 conditions this grows out of control):
IIF(Eq([//Target/Code1],True),IIF(Eq([//Target/Code2],True),IIF(Eq([//Target/Code3],True),"1,2,3","1,2") ,IIF(Eq([//Target/Code3],True),"1,3","1") )
,IIF(Eq([//Target/Code2],True),IIF(Eq([//Target/Code3],True),"2,3","2") ,IIF(Eq([//Target/Code3],True),"3","") ))
OR you can use one of these custom workflows that allows you to run your own code:
http://fimwf.codeplex.com/
or
https://fimactivitylibrary.codeplex.com/wikipage?title=Code%20Run%20samples&referringTitle=Documentation
David Lundell, Get your copy of FIM Best Practices Volume 1 http://blog.ilmbestpractices.com/2010/08/book-is-here-fim-best-practices-volume.html