anchor.diff: -{ lib, stdenv, fetchFromGitHub, cmake, fmt_8, fetchpatch }:
  +{ lib, stdenv, fetchFromGitHub, cmake, fmt_8 }:
   
   let
  -  generic = { version, sha256, patches ? [] }:
  +  generic = { version, sha256 }:
       stdenv.mkDerivation {
         pname = "spdlog";
         inherit version;
  
positive.code: in
  {
    spdlog_1 = generic {
      version = "1.9.2";
      sha256 = "sha256-GSUdHtvV/97RyDKy8i+ticnSlQCubGGWHg4Oo+YAr8Y=";
      patches = [
        # glibc 2.34 compat
        (fetchpatch {
          url = "https://github.com/gabime/spdlog/commit/d54b8e89c058f3cab2b32b3e9a2b49fd171d5895.patch";
          sha256 = "sha256-pb7cREF90GXb5Mbs8xFLQ+eLo6Xum13/xYa8JUgJlbI=";
        })
      ];
    };
  
    spdlog_0 = generic {
  
negative.code:         rev    = "v${version}";
          inherit sha256;
        };
  
        nativeBuildInputs = [ cmake ];
        # spdlog <1.3 uses a bundled version of fmt
  