An implementation of the simply-typed lambda calculus and
equality on well-typed terms.  This gives a declaration and
and implementation of equality and shows that the implementation
is sound (but does not show that it is complete).  The code is
described in the paper cited below.

Author: Frank Pfenning.

Reference: Frank Pfenning: Logic Programming in the LF Logical Framework.
In: Logical Frameworks, Gerard Huet and Gordon D. Plotkin (eds.),
Cambridge University Press, 1991.
