Solver-agnostic symbolic values support for issuing queries

 What4 is a generic library for representing values as symbolic formulae which
 may contain references to symbolic values, representing unknown variables.
 It provides support for communicating with a variety of SAT and SMT solvers,
 including Z3, CVC4, CVC5, Yices, Boolector, STP, and dReal.
 The data representation types make heavy use of GADT-style type indices
 to ensure type-correct manipulation of symbolic values.
 .
 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.