[Add URLs for prolog, background, etc.] "Programming in Logic", a declarative language (sort of) popular in Europe. See Playing Prolog and Playing predicate logic.

SICSTus Prolog has a bi-directional Tcl interface: [L1 ].

Also ECLiPSe (not to be mistaken with the IDE [L2 ]) has an interface to Tcl/Tk [L3 ]. A description and some first steps are listed at ECLiPSe_CLP.

Haven't there been collaborations between Prolog and Tk?