hz3: Bindings for the Z3 Theorem Prover

[ bit-vectors, bsd3, deprecated, formal-methods, library, math, smt, theorem-provers ] [ Propose Tags ]

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Bindings for the Z3 4.x Theorem Prover (https://github.com/Z3Prover/z3).

  • Z3.Base.C provides the raw foreign imports from Z3's C API.

  • Z3.Base does the marshaling of values between Haskell and C, and transparently handles reference counting of Z3 objects for you.

  • Z3.Monad provides a convenient monadic wrapper for the common usage scenario.

Examples: https://github.com/strake/z3.hs/tree/master/examples

Changelog: https://github.com/strake/z3.hs/blob/master/CHANGES.md


  • Unix-like: Just be sure to use the standard locations for dynamic libraries (/usr/lib) and header files (/usr/include), or else use the --extra-lib-dirs and --extra-include-dirs Cabal flags.

(Hackage reports a build failure because Z3's library is missing.)

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Manual Flags


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Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info


Note: This package has metadata revisions in the cabal description newer than included in the tarball. To unpack the package including the revisions, use 'cabal get'.

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Versions [RSS]
Change log CHANGES.md
Dependencies base (>=4.5 && <5), containers, transformers (>=0.2) [details]
License BSD-3-Clause
Copyright 2012-2018, Iago Abal, David Castro
Author Iago Abal <mail@iagoabal.eu>, David Castro <david.castro.dcp@gmail.com>
Maintainer none
Revised Revision 3 made by MatthewFarkasDyck at 2020-03-13T20:44:49Z
Category Math, SMT, Theorem Provers, Formal Methods, Bit vectors
Home page https://github.com/strake/z3.hs
Bug tracker https://github.com/strake/z3.hs
Source repo head: git clone https://github.com/strake/z3.hs
Uploaded by MatthewFarkasDyck at 2019-10-01T01:07:27Z
Distributions NixOS:
Executables examples
Downloads 593 total (5 in the last 30 days)
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Status Docs uploaded by user [build log]
All reported builds failed as of 2019-10-01 [all 3 reports]

Readme for hz3-

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Haskell bindings for Microsoft's Z3 (unofficial)

These are Haskell bindings for the Z3 theorem prover. We don't provide any high-level interface (e.g. in the form of a Haskell eDSL) here, these bindings are targeted to those who want to build verification tools on top of Z3 in Haskell.

Changelog here.

Examples here.

Do you want to contribute?


Preferably use the z3 package.

  • Install a Z3 4.8.x release.

  • Just type cabal install z3 if you used the standard locations for dynamic libraries (/usr/lib) and header files (/usr/include).

    • Otherwise use the --extra-lib-dirs and --extra-include-dirs Cabal flags when installing.


Most people uses the Z3.Monad interface. Here is an example script that solves the 4-queen puzzle:

import Control.Applicative
import Control.Monad ( join )
import Data.Maybe
import qualified Data.Traversable as T

import Z3.Monad

script :: Z3 (Maybe [Integer])
script = do
  q1 <- mkFreshIntVar "q1"
  q2 <- mkFreshIntVar "q2"
  q3 <- mkFreshIntVar "q3"
  q4 <- mkFreshIntVar "q4"
  _1 <- mkInteger 1
  _4 <- mkInteger 4
  -- the ith-queen is in the ith-row.
  -- qi is the column of the ith-queen
  assert =<< mkAnd =<< T.sequence
    [ mkLe _1 q1, mkLe q1 _4  -- 1 <= q1 <= 4
    , mkLe _1 q2, mkLe q2 _4
    , mkLe _1 q3, mkLe q3 _4
    , mkLe _1 q4, mkLe q4 _4
  -- different columns
  assert =<< mkDistinct [q1,q2,q3,q4]
  -- avoid diagonal attacks
  assert =<< mkNot =<< mkOr =<< T.sequence
    [ diagonal 1 q1 q2  -- diagonal line of attack between q1 and q2
    , diagonal 2 q1 q3
    , diagonal 3 q1 q4
    , diagonal 1 q2 q3
    , diagonal 2 q2 q4
    , diagonal 1 q3 q4
  -- check and get solution
  fmap snd $ withModel $ \m ->
    catMaybes <$> mapM (evalInt m) [q1,q2,q3,q4]
  where mkAbs x = do
          _0 <- mkInteger 0
          join $ mkIte <$> mkLe _0 x <*> pure x <*> mkUnaryMinus x
        diagonal d c c' =
          join $ mkEq <$> (mkAbs =<< mkSub [c',c]) <*> (mkInteger d)

In order to run this SMT script:

main :: IO ()
main = evalZ3 script >>= \mbSol ->
        case mbSol of
             Nothing  -> error "No solution found."
             Just sol -> putStr "Solution: " >> print sol