anchor.diff:      configureFlagsArray=(
         $configureFlagsArray
         "--CC=$CC"
  -      "--with-cxx=0"
  +      "--with-cxx=g++"
         "--with-fc=0"
         "--with-mpi=0"
         "--with-blas-lib=[${blas}/lib/libblas.a,${gfortran.cc.lib}/lib/libgfortran.a]"
  
positive.code:     )
    '';
  
    postInstall = ''
      rm $out/bin/petscmpiexec
      rm $out/bin/popup
      rm $out/bin/uncrustify.cfg
      rm -rf $out/bin/win32fe
    '';
  
    meta = {
      description = "Library of linear algebra algorithms for solving partial differential equations";
      homepage = https://www.mcs.anl.gov/petsc/index.html;
      platforms = stdenv.lib.platforms.all;
      license = stdenv.lib.licenses.bsd2;
    };
  }
  
negative.code: { stdenv , fetchurl , blas , gfortran , liblapack , python }:
  
  stdenv.mkDerivation rec {
    pname = "petsc";
    version = "3.12.4";
  
    src = fetchurl {
      url = "http://ftp.mcs.anl.gov/pub/petsc/release-snapshots/petsc-${version}.tar.gz";
      sha256 = "1hw4f12v2xwrs37gjh83dbixhg0yxandqx7s7k5vlfx91l9l3aan";
    };
  
    nativeBuildInputs = [ blas gfortran.cc.lib liblapack python ];
  