SZ stands for Serguey Zefirov.I am a 33-year old Tcl and other languages hacker from Russia.Right now it is my job to hack Tcl, around Tcl and with Tcl.Most of my recent programs are all done in Tcl.Right now I am unemployed but busy.I, for long time, was fascinated with Functional Programming languages, especially Haskell (see Playing Haskell) (actually, I found Tcl/Tk trying to start up FranTk - Haskell declarative GUI library on top of Tk). So I decided to reproduce its useful feature, called Algebraic Types.To further demonstrate Algebraic Types I wrote Simple BDD and adapt Expression Tree Package from same code in Haskell.