anchor.diff:  
     ## Named versions corresponding to some builtin operators.
   
  -  /* Concat two strings */
  +  /* Concatenate two lists */
     concat = x: y: x ++ y;
   
     /* boolean “or” */
  
positive.code:     isInt isFloat add sub lessThan
      seq deepSeq genericClosure;
  
    inherit (lib.strings) fileContents;
  
    release = fileContents ../.version;
    versionSuffix = let suffixFile = ../.version-suffix; in
      if pathExists suffixFile then fileContents suffixFile else "pre-git";
  
    # Return the Nixpkgs version number.
    version = release + versionSuffix;
  
    nixpkgsVersion = builtins.trace "`lib.nixpkgsVersion` is deprecated, use `lib.version` instead!" version;
  
    # Whether we're being called by nix-shell.
    inNixShell = builtins.getEnv "IN_NIX_SHELL" != "";
  
    # Return minimum/maximum of two numbers.
    min = x: y: if x < y then x else y;
  
negative.code:        => 1
    */
    mod = base: int: base - (int * (builtins.div base int));
  
  
    ## Comparisons
  
    /* C-style comparisons
  
  