anchor.diff:    pname = "sundials";
     version = "5.3.0";
   
  -  buildInputs = [ python ] ++ stdenv.lib.optionals (lapackSupport) [ gfortran blas lapack ];
  +  buildInputs = [
  +    python
  +  ] ++ stdenv.lib.optionals (lapackSupport) [
  +    gfortran
  +    blas
  +    lapack
  +  ] 
  +  # KLU support is based on Suitesparse.
  +  # It is tested upstream according to the section 1.1.4 of
  +  # [INSTALL_GUIDE.pdf](https://raw.githubusercontent.com/LLNL/sundials/master/INSTALL_GUIDE.pdf)
  +  ++ stdenv.lib.optionals (kluSupport) [
  +    suitesparse
  +  ];
  +
     nativeBuildInputs = [ cmake ];
   
     src = fetchurl {
  
positive.code:     "-DSUNDIALS_INDEX_TYPE=int32_t"
      "-DLAPACK_ENABLE=ON"
      "-DLAPACK_LIBRARIES=${lapack}/lib/liblapack${stdenv.hostPlatform.extensions.sharedLibrary}"
    ];
  
    doCheck = true;
  
negative.code: , blas
  , lapack
  , gfortran
  , suitesparse
  , lapackSupport ? true
  , kluSupport ? true }:
  
  assert (!blas.isILP64) && (!lapack.isILP64);
  
  