Apia

Description

Apia is a Haskell program for proving first-order theorems written in Agda using automatic theorem provers for first-order logic (ATPs). Before calling the ATPs, the Agda formulae are translated into TPTP language.

Apia is used for reasoning about functional programs by combining interactive and automatic proofs (see README.md).

Prerequisites

• Glasgow Haskell Compiler (GHC)

  Apia supports the versions of GHC supported by Agda upstream, i.e. 7.10.3, 8.0.2, 8.2.2 and 8.4.3.

  Check your version with:

  $ ghc --version

• Extended version of Agda

  We have extended the development version of Agda in order to handle the new built-in ATP-pragma. This extended version of Agda is required by the Apia program.

• ATPs: Apia can use offline or online ATPs

  • Offline ATPs

    The currently supported offline ATPs are:

    ATP	Tested version
    CVC4	CVC4 1.6
    E	E 2.1 Maharani Hills
    Equinox	Equinox 5.0alpha (2010-06-29)
    ileanCoP	ileanCoP 1.3beta1
    Metis	Metis 2.4 (release 20180301)
    SPASS	SPASS V 3.9
    Vampire	Vampire 0.6 (revision 903)
    Z3	Z3 version 4.5.0 - 64 bit

  • Online ATPs

    Apia can use any online ATP available in the TPTP World by using the online-atps program.

• The tptp4X program

  The --check command-line option or using Z3 as a first-order ATP require the tptp4X program from the TPTP library. This program is included in this repository. The tested version of tptp4X is 6.4.0.2 from Geoff's Service Tools.

Installation

1. Extended version of Agda (see README.md)

2. The Apia program

   You can download the Apia program using Git. The program can be downloaded and installed with the following commands:

   $ git clone https://github.com/asr/apia.git
   $ cd apia
   $ cabal install

   In order to test the installation of Apia, you can try to automatically prove the conjecture in

   module Test where
   
   data _∨_ (A B : Set) : Set where
     inj₁ : A → A ∨ B
     inj₂ : B → A ∨ B
   
   postulate
     A B    : Set
     ∨-comm : A ∨ B → B ∨ A
   {-# ATP prove ∨-comm #-}

   using the E ATP by running the following commands:

   $ agda Test.agda
   $ apia --atp=e Test.agda
   Proving the conjecture in /tmp/Test/9-8744-comm.tptp ...
   E 2.1 Maharani Hills proved the conjecture

   Apia will call the E ATP and tell if this ATP was able to prove the conjecture. If the ATP could not prove the conjecture after the default timeout, the process of proving that particular conjecture is aborted.

Using online ATPs

After installing the online-atps tool from this repository, it is possible to use any ATP available on SystemOnTPTP.

For example, we could use an online version of the E ATP using the following commands:

$ apia --atp=online-e Test.agda
Proving the conjecture in /tmp/Test/9-8744-comm.tptp ...
E-2.0 proved the conjecture

To see a list of all online ATPs available, run the following command:

$ online-atps --list-atps

YAML Configuration

We can run Apia using options set in YAML files with name .apia. The options break down into project-specific options in:

• <project dir>/.apia

and non-project-specific options in:

• ~/.apia -- for user non-project default options

Note: When Apia is invoked outside a project it will source project specific options from ~/.apia. Options in this file will be ignored for a project with its own <project dir>/.apia.

Project-specific config

Project-specific options are only valid in the .apia file local to a project, not in the user config files.

Note: We define project to mean a directory that contains an .apia file, which specifies valid options. The options are specified in the help command. Check apia --help to see all options available.

In your project-specific options, you specify which options to use when running Apia.

Examples

We want to use the ATPs E, Metis and the online version of Vampire with Apia. Also, we want to save the results in the directory /myoutputdir and use the option check. Then, our Apia file should be similar to this one.

# cat ~/.apia
atp: ["e", "metis", "online-vampire"]
output-dir: "/myoutputdir"
check: true

Known limitations

• Logical symbols

  The following symbols are hard-coded, i.e. they should be used: ⊥ (falsehood), ⊤ (truth), ¬_ (negation), _∧_ (conjunction), _∨_ (disjunction), the Agda non-dependent function type → (implication), _↔_ (equivalence), the Agda dependent function type (x : A) → B (universal quantifier) and ∃ (existential quantifier).

• Agda version

  The Apia program must be compiled using the same version of Agda that was used to generate the Agda interface files.