anchor.diff:  
     pythonmagick = import ../applications/graphics/PythonMagick {
       inherit fetchurl stdenv pkgconfig imagemagick boost;
  -    python = python_alts.v_2_5;
  +    python = builtins.getAttr "2.5" python_alts;
     };
   
     qemuFun = lib.sumArgs (selectVersion ../applications/virtualization/qemu ) {
  
positive.code: 
    pyrexFun = lib.sumArgs (selectVersion ../development/interpreters/pyrex) {
      inherit fetchurl stdenv stringsWithDeps lib builderDefs;
      python = python_alts.v_2_5;
    };
  
    pyrex = pyrexFun {version = "0.9.6";} null;
  
negative.code: 
    qcmm = import ../development/compilers/qcmm {
      lua   = lua4;
      ocaml = builtins.getAttr "3.08.0" ocaml_alts;
      inherit fetchurl stdenv mk noweb groff;
    };
  
  