Issue with in-line logical operation to fill text wave

I am trying to do a logical operation in line to fill a text wave.

This compiles ...

	make/N=(npts)/FREE rwstr	
	rwstr = (cmpstr(fstr[p],lstr[p])==0) ? 1 : 0

This does not compile ...

	make/N=(npts)/FREE/T rwstr	
	rwstr = (cmpstr(fstr[p],lstr[p])==0) ? "a" : "b"

I am using Igor Pro 8.

you can use SelectString(conditional, falsestring, truestring) instead of  conditional ? true : false