anchor.diff:             {{t,11},2},
              {{t,12},4},
              {{t,13},1}] =
  -        analyse_expr(<<"<< \n" % 1 (now: 0)
  +        analyse_expr(<<"<< \n" % 1
                          " << (2)\n" % 4 (now: 0)
                          "     :(8) >> || \n"
                          "    <<X>> <= << 1,\n" % 1
  
positive.code:                        "    true >>.\n" % 2
                         "two() -> 2">>, Cf),
  
      ?line [% {{t,1},1},
             %% {{t,2},4},
             {{t,4},1},
             {{t,6},1},
  
negative.code:            {{t,12},3},
             {{t,13},2},
             {{t,14},2}] = 
          analyse_expr(<<"<< \n" % 1
                         " << (X*2) >> || \n" % 2 (now: 0)
                         "    <<X>> <= << (case two() of\n"
                         "                     2 -> 1;\n" % 1
  