anchor.diff:  , enableStatic ? false
   , enablePIC ? false
   , enableExceptions ? false
  +, taggedLayout ? ((enableRelease && enableDebug) || (enableSingleThreaded && enableMultiThreaded) || (enableShared && enableStatic))
   }:
   
   let
  
positive.code:   configureScript = "./bootstrap.sh";
    configureFlags = "--with-icu=${icu} --with-python=${python}/bin/python";
  
    buildPhase = "./b2 -j$NIX_BUILD_CORES -sEXPAT_INCLUDE=${expat}/include -sEXPAT_LIBPATH=${expat}/lib --layout=${finalLayout} variant=${variant} threading=${threading} link=${link} ${cflags} install";
  
    installPhase = ":";
  
  
negative.code:      stdenv.lib.optional enableStatic "static");
  
    # To avoid library name collisions
    layout = if taggedLayout then "tagged" else "system";
  
    cflags = if (enablePIC && enableExceptions) then
               "cflags=-fPIC -fexceptions cxxflags=-fPIC linkflags=-fPIC"
  