`ogma-core`: equivalence operator should be translated to `(==)`

[Andersen0]

When using an equivalence operator (as used in, for example, FRETISH requirements as <=>) the returned Monitor will not be able to properly run because the Haskell Monitor cannot use the <==> operator that is defined in the code.

The command used for generation of the Monitor was: _ogma fret-component-spec --fret-file-name fretspecifications.json > Monitor.hs

The command used for compiling and linking: ghc -package copilot-c99 -package copilot-language -package copilot-libraries Monitor.hs

Acquired error message:

Variable not in scope:
      (<==>) :: Stream Bool -> Stream Bool -> Stream Bool
    Suggested fix: Perhaps use ‘==>’ (imported from Copilot.Language)

Suggested fix: Defining a custom infix operator that compares two boolean arguments and returns true if they are both true or both false

infix 4 <==>
(<==>) :: Stream (Bool) -> Stream (Bool) -> Stream (Bool)
a <==> b = a == b

[ivanperez-keera]

Thank you @Andersen0 . I can confirm that the issue is there. This will be an easy fix.

[ivanperez-keera]

Description

The SMV to Copilot translator translates equivalences as (<==>). However, that operator does not exist in Copilot, it is simply (==) for Bools.

Type

• Bug: backend generates incorrect code.

Additional context

None.

Requester

• Tage Andersen and Elias Evjen Hartmark (NMBU, Norway)

Method to check presence of bug

Compiling a specification with <-> in the ptLTL field produces Copilot code that does not compile:

{
  "test_componentSpec": {
    "Functions": [
    ],
    "Internal_variables": [
    ],
    "Other_variables": [
      {
        "name": "a",
        "type": "bool"
      }
    ],
    "Requirements": [
      {
        "CoCoSpecCode": "true",
        "fretish": "unimportant",
        "name": "testCopilot001",
        "ptLTL": "a <-> a"
      }
    ]
  }
}

    • Variable not in scope:
        (<==>) :: Stream Bool -> Stream Bool -> Stream Bool
    • Perhaps you meant ‘==>’ (imported from Copilot.Language)
   |
20 | propTestCopilot001 = (a <==> a)

Expected result

The execution above should produce a Copilot specification that can be compiled and where == is used in Copilot where an equivalence between booleans needs to be expressed.

Desired result

The execution above should produce a Copilot specification that can be compiled and where == is used in Copilot where an equivalence between booleans needs to be expressed.

Proposed solution

Modify the SMV translator to use (==) instead of <==>.

Further notes

None.

[ivanperez-keera]

Change Manager: Confirmed that the issue exists.

[ivanperez-keera]

Technical Lead: Confirmed that the issue should be addressed.

[ivanperez-keera]

Technical Lead: Issue scheduled for fixing in Ogma 1.3.

Fix assigned to: @ivanperez-keera.

[ivanperez-keera]

Implementor: Solution implemented, review requested.

[ivanperez-keera]

Change Manager: Verified that:

• Solution is implemented:

  • [X] The code proposed compiles passes the tests. Details: Docker image:

    
    FROM ubuntu:trusty

  RUN apt-get update

  RUN apt-get install --yes software-properties-common RUN add-apt-repository ppa:hvr/ghc RUN apt-get update

  RUN apt-get install --yes ghc-8.6.5 cabal-install-2.4 RUN apt-get install --yes libz-dev

  ENV PATH=/opt/ghc/8.6.5/bin:/opt/cabal/2.4/bin:$PWD/.cabal-sandbox/bin:$PATH

  RUN cabal update RUN cabal v1-sandbox init RUN cabal v1-install alex happy RUN apt-get install --yes git

  We install the application first and then test it, in case any tests need to

  run the tool.

  CMD git clone $REPO && \ cd $NAME && \ git checkout $COMMIT && \ cd .. && \ cabal v1-install $NAME/$PAT/ --enable-tests && \ cabal v1-install $NAME/$PAT/ --enable-tests --run-tests -j1

  Command:
  ```sh
  $ docker run -e "REPO=https://github.com/nasa/ogma" -e "NAME=ogma" -e PAT="ogma-" -e "COMMIT=d3ebffca2227cd61e1ea3e520fb5610f487e3633" -it ogma-test

  • [X] The solution proposed fixes the issues described. Details: The following Dockerfile uses the spec containing an equivalence operator in the SMV property, and it compiles the resulting Copilot code.

    
    --- Dockerfile-verify-126
    FROM ubuntu:trusty

  ENV DEBIAN_FRONTEND=noninteractive

  RUN apt-get update

  RUN apt-get install --yes software-properties-common RUN add-apt-repository ppa:hvr/ghc RUN apt-get update

  RUN apt-get install --yes ghc-8.6.5 cabal-install-2.4 RUN apt-get install --yes libz-dev

  ENV PATH=/opt/ghc/8.6.5/bin:/opt/cabal/2.4/bin:$PWD/.cabal-sandbox/bin:$PATH

  RUN cabal update RUN cabal v1-sandbox init RUN cabal v1-install alex happy RUN cabal v1-install copilot-3.18.1 RUN apt-get install --yes git

  ADD reqs.json /tmp/reqs.json

  CMD git clone $REPO && \ cd $NAME && \ git checkout $COMMIT && \ cd .. && \ cabal v1-install $NAME/$PAT**/ && \ ogma fret-component-spec --fret-file-name /tmp/reqs.json > CS.hs && \ cabal v1-exec -- ghc --make CS.hs && \ echo "Success"

  --- reqs.json { "test_spec": { "Functions": [ ], "Internal_variables": [ ], "Other_variables": [ { "name": "a", "type": "bool" } ], "Requirements": [ { "CoCoSpecCode": "true", "fretish": "unimportant", "name": "testCopilot001", "ptLTL": "a <-> a" } ] } }

  Command:
  ```sh
  $ docker run -e "REPO=https://github.com/nasa/ogma" -e "NAME=ogma" -e PAT="ogma-" -e "COMMIT=d3ebffca2227cd61e1ea3e520fb5610f487e3633" -it ogma-verify-126

• [X] Implementation is documented. Details: No changes needed.
• [X] Change history is clear.
• [X] Commit messages are clear.
• [X] Changelogs are updated.
• [X] Examples are updated. Details: No examples affected.
• [X] Required version bumps are evaluated. Details: No bump needed (internal change).

[ivanperez-keera]

Change Manager: Implementation ready to be merged.