This section explains basic principles of the Tcl language. It is meant mainly for Tcl beginners to allow them a smooth start into Tcl programming. Experts can simply skip this section. As this manual is intended mainly for Prolog programmers, we try to point out differences between the two languages and how they are handled inside ProTcXl .
Tcl is a scripting language with a simple and consistent structure. It is an interpreted language and it can be executed either by the shell program tclsh, which contains only the Tcl part, by the window shell wish which also contains the Tk toolkit, or from the Prolog top-level loop or a Prolog program. Both tclsh and wish read commands from the standard input, evaluate them and print the result. We use their output for examples throughout this paper:
lyra% tclsh % set argc 0