[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: [1].

Also ECLiPSe (not to be mistaken with the IDE [2]) has an interface to Tcl/Tk [3]. A description and some first steps are listed at ECLiPSe_CLP.

Haven't there been collaborations between Prolog and Tk?

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