anchor.diff: -{ lib, stdenv, fetchFromGitHub, cmake
  +{ lib, stdenv, fetchFromGitHub, fetchpatch, cmake
   , gfortran, blas, lapack, eigen }:
   
   stdenv.mkDerivation rec {
     pname = "arpack";
  -  version = "3.7.0";
  +  version = "3.8.0";
   
     src = fetchFromGitHub {
       owner = "opencollab";
       repo = "arpack-ng";
       rev = version;
  -    sha256 = "1x7a1dj3dg43nlpvjlh8jzzbadjyr3mbias6f0256qkmgdyk4izr";
  +    sha256 = "sha256-nc710iLRqy/p3EaVgbEoCRzNJ9GpKqqQp33tbn7R6lA=";
     };
  +
  +  patches = [
  +    # https://github.com/opencollab/arpack-ng/pull/301
  +    (fetchpatch {
  +      name = "pkg-config-paths.patch";
  +      url = "https://github.com/opencollab/arpack-ng/commit/47fc83cb371a9cc8a8c058097de5e0298cd548f5.patch";
  +      excludes = [ "CHANGES" ];
  +      sha256 = "1aijvrfsxkgzqmkzq2dmaj8q3jdpg2hwlqpfl8ddk9scv17gh9m8";
  +    })
  +  ];
   
     nativeBuildInputs = [ cmake ];
     buildInputs = assert (blas.isILP64 == lapack.isILP64); [
  
positive.code: 
    cmakeFlags = [
      "-DBUILD_SHARED_LIBS=ON"
      "-DINTERFACE64=${lib.optionalString blas.isILP64 "1"}"
    ];
  
    preCheck = if stdenv.isDarwin then ''
  
negative.code:       problems.
      '';
      license = lib.licenses.bsd3;
      maintainers = with lib.maintainers; [ ttuegel dotlambda ];
      platforms = lib.platforms.unix;
    };
  }
  