sml_tk is a Standard ML package that provides a portable, typed and abstract interfce to the user interface and description language Tcl/Tk. This allows reusable programming of Graphical User Interfaces in a structured way, supported by the powerful module system of SML. Part of the sml_tk package is a library of standard components; in particular, the highly generic graphical user interface GenGUI, that has been instantiated for several theorem prover applications.

This report presents an introduction, design description and a reference manual for sml_tk.