Sidekick is an OCaml library for creating SMT solvers following the CDCL(T) approach (so called "lazy SMT"). See below for a more detailed explanation.

It derives from Alt-Ergo Zero and its fork mSAT.

See the API documentation.

A work-in-progress guide provides a more step-by-step introduction to how to use and modify sidekick.

SMT solvers are automatic tools that try to assess whether a given logic formula is satisfiable (admits a model, an interpretation that makes it true) or unsatisfiable (no interpretation can make it true; it is absurd, and its negation is a theorem). Prominent solvers include Z3, cvc5, Yices 2, and others; all of them follow the CDCL(T) paradigm. Most of these solvers are implemented in C or C++.

CDCL(T) is the combination of CDCL, the leading technique for SAT solving (as popularized by Chaff, minisat, etc. in the early oughties), and a theory T. In practice, SMT solvers combine multiple theories into one before doing the combination with the SAT solver. Some examples of theories are uninterpreted functions symbols, integer linear arithmetic ("LIA"), rational nonlinear arithmetic ("NRA"), bitvectors for fixed-size arithmetic, algebraic datatypes, and others.

Sidekick is a CDCL(T) solver implemented in pure OCaml and with a strong focus on modularity and reusability of components. It used to provide a functorized interface, but it now comes with its own representation of terms, in a simple version of the Calculus of Constructions. Users can extend that term representation by adding new custom constants to model their domain theories. Most of the constants defined in sidekick are defined exactly as outside constants would be.

Sidekick comes in several components (as in, opam packages):

• sidekick is the core library, with core type definitions (see src/core/), an implementation of CDCL(T) based on mSat, a congruence closure, and the theories of boolean formulas, LRA (linear rational arithmetic, using a simplex algorithm), and datatypes.
• sidekick-base is a library with concrete implementations for terms, arithmetic functions, and proofs. It comes with an additional dependency on zarith to represent numbers (zarith is a GMP wrapper for arbitrary precision numbers).
• sidekick-bin is an executable that is able to parse problems in the SMT-LIB-2.6 format, in the QF_UFLRA fragment, and solves them using sidekick instantiated with sidekick-base. It is mostly useful as a test tool for the libraries and as a starting point for writing custom solvers.

Once the package is on opam, just opam install sidekick. For the development version, use:

opam pin https://github.com/c-cube/sidekick.git

You will need dune . The command is:

make install

This program is distributed under the Apache Software License version 2.0. See the enclosed file LICENSE.