sbvPlugin

Formally prove properties of Haskell programs using SBV/SMT http://github.com/LeventErkok/sbvPlugin

Latest on Hackage:0.10

This package is not currently in any snapshots. If you're interested in using it, we recommend adding it to Stackage Nightly. Doing so will make builds more reliable, and allow stackage.org to host generated Haddocks.

BSD3 licensed by Levent Erkok
Maintained by Levent Erkok (erkokl@gmail.com)

SBVPlugin: SBV Plugin for GHC

Hackage version Build Status

Example

{-# OPTIONS_GHC -fplugin=Data.SBV.Plugin #-}

module Test where

import Data.SBV.Plugin

test :: Proved (Integer -> Integer -> Bool)
test x y = x + y >= x - y

Note the GHC option on the very first line. Either add this to your file, or pass -fplugin=Data.SBV.Plugin as an argument to GHC, either on the command line or via cabal. Same trick also works for GHCi.

The Proved type simply wraps over the type of the predicate you are trying to prove, typically a function returning a Bool value. It tells the plugin to treat the input as a theorem that needs to be proved. When compiled, we get:

$ ghc -c Test.hs

[SBV] Test.hs:8:1-4 Proving "test", using Z3.
[Z3] Falsifiable. Counter-example:
  x =  0 :: Integer
  y = -1 :: Integer
[SBV] Failed. (Use option 'IgnoreFailure' to continue.)

Note that the compilation will be aborted, since the theorem doesn't hold. If you load this file in GHCi, it will simply fail and drop you back to the GHCi prompt.

Annotation style

While the Proved type should suffice for simple uses, the plugin takes a number of arguments to modify options and pick underlying solvers. In this case, an explicit annotation can be provided:

{-# OPTIONS_GHC -fplugin=Data.SBV.Plugin #-}

module Test where

import Data.SBV.Plugin

{-# ANN test theorem {options = [IgnoreFailure]} #-}
test :: Integer -> Integer -> Bool
test x y = x == y -- clearly not True!

The above, for instance, tells the plugin to ignore failed proofs (IgnoreFailure). This is useful when you have a failing theorem that you are still working on, to make sure GHC continues compilation instead of stopping compilation and erroring out at that point.

Available options

The plugin currently understands the following options. Multiple options can be given at the same time by comma separating them.

data SBVOption =
   IgnoreFailure  -- ^ Continue even if proof fails
 | Skip String    -- ^ Skip the proof. Can be handy for properties that we currently do not want to focus on.
 | Verbose        -- ^ Produce verbose output, good for debugging
 | Debug          -- ^ Produce really verbose output, use only when things go really wrong!
 | QuickCheck     -- ^ Perform quickCheck
 | Uninterpret    -- ^ Uninterpret this binding for proof purposes
 | Names [String] -- ^ Use these names for the arguments; need not be exhaustive
 | ListSize Int   -- ^ If a list-input is found, use this length. If not specified, we will complain!
 | Z3             -- ^ Use Z3
 | Yices          -- ^ Use Yices
 | Boolector      -- ^ Use Boolector
 | CVC4           -- ^ Use CVC4
 | MathSAT        -- ^ Use MathSAT
 | ABC            -- ^ Use ABC
 | AnySolver      -- ^ Run all installed solvers in parallel, and report the result from the first to finish

Using SBVPlugin from GHCi

The plugin should work from GHCi with no changes. Note that when run from GHCi, the plugin will behave as if the IgnoreFailure argument is given on all annotations, so that failures do not stop the load process.

Thanks

The following people reported bugs, provided comments/feedback, or contributed to the development of SBVPlugin in various ways: Nickolas Fotopoulos and Stephan Renatus.

Changes

Version 0.10, Not yet released

  • Changes required to compile with GHC 8.2.1.

Version 0.9, 2017-07-19

  • Sync-up with recent modifications to SBV. No user visible changes.
  • Bump up sbv dependence to >= 7.0

Version 0.8, 2017-01-12

  • Fix broken links, thanks to Stephan Renatus for the patch.
  • Add the 'Proved' type, which allows for easily tagging a type for proof, without the need for an explicit annotation. Thanks to Nickolas Fotopoulos for the patch.
  • Bump up sbv dependence to >5.14

Version 0.7, 2016-06-06

  • Compile with GHC-8.0. Plugin at least requires GHC-8.0.1 and SBV 5.12
  • Fix a few dead links

Version 0.6, 2016-01-01

  • Support for list expressions of the form [x .. y] and [x, y .. z]; so long as the x, y, and z are all concrete.
  • Simplify some of the expressions in BitTricks using the new list-construction support.
  • Added more proofs to the BitTricks example

Version 0.5, 2015-12-26

  • Allow higher-order (i.e., function) arguments to theorems.
  • Rework uninterpreted functions, generalize types
  • Simplify cabal file; no need to ship gold-files for tests
  • Add merge-sort example "Data/SBV/Plugin/Examples/MergeSort.hs"
  • Add bit-tricks example "Data/SBV/Plugin/Examples/BitTricks.hs"

Version 0.4, 2015-12-24

  • Support for case-alternatives producing lists/tuples and functions. In the list case, we require that both alternatives produce equal-length lists, as otherwise there is no way to merge the two results.
  • More test cases.

Version 0.3, 2015-12-21

Version 0.2, 2015-12-21

  • Further fleshing of internals
  • Support for case-expressions
  • Support for uninterpreted types/functions
  • Lots of test cases, refactoring.

Version 0.1, 2015-12-06

  • Basic functionality. Initial design exploration.
  • The plugin functional on base values, but there are a lot of rough edges around the details. Please report any issues you might find!
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