anchor.diff:    };
   
     preConfigure = ''
  +    # To avoid problems due to libc++abi 11 using `#include <version>`.
       rm version
  -    aclocal
     '';
   
     buildInputs = with lib;
  
positive.code: { lib, stdenv, fetchurl, mecab, kytea, libedit, pkg-config
  , suggestSupport ? false, zeromq, libevent, msgpack
  , lz4Support  ? false, lz4
  , zlibSupport ? false, zlib
  , autoconf, automake
  }:
  
  stdenv.mkDerivation rec {
  
negative.code:     ++ optional zlibSupport zlib
      ++ optionals suggestSupport [ zeromq libevent msgpack ];
  
    nativeBuildInputs = [ autoreconfHook pkg-config ];
  
    configureFlags = with lib;
         optional zlibSupport "--with-zlib"
  