Elf implementation of Pfenning & Wong's modal lambda-calculus for S4.  

Andrzej Filinski, Nov.'94

README		This file
syntax.elf	Approximately-typed HOAS for both calculi (static)
modality.elf	Checking of modality restrictions (for both calculi)
trans.elf	Translation from explicit to implicit system
compl.elf	Completeness of implicit system wrt. explicit
canon.elf	Conversion to canonical form of approximately-typed terms
lemmas.elf	Admissibility of reflexivity and transitivity of reachability
tpres.elf	Preservation of (strict) typing for conversion to canonical
igen.elf	Iterative-deepening generator of implicit terms (for testing)
examples.quy	A couple of illustrative examples (not comprehensive)
load.sml	SML loader for Elf files
itrans.sml	Translation from implicit to explicit system (in SML)

hoas.sml	A few experimets with higher-order abstract syntax
		as an "inductive datatype" in SML.
