float comparison for range value fails

[alexxcons]

fel0021(triggered ps3000 scope) currently fails to run, even though the selected range 0.05 (50 mV in the flowgraph) is valid.

The reason seems to be that floating-point comparison should better not be done with ==, since already minimal discrepancies (for whatever reason) lead to a mismatch.

Edit: Problem is, that partly double and partly float is used to store the "range", which leads to conversion errors. Using the same type in all places fixes the problem.

Though a much more failsafe way would be the usage of an enum, like e.g. done for coupling (check for coupling_t).

Here the currently used code which throws an expetion, when "0.05" is passed due to floating point comparison:

    static PS3000A_RANGE
    convert_to_ps3000a_range(float range)
    {
      if (range == 0.01)
        return PS3000A_10MV;
      else if (range == 0.02)
        return PS3000A_20MV;
      else if (range == 0.05)
        return PS3000A_50MV;
      else if (range == 0.1)
        return PS3000A_100MV;
      else if (range == 0.2)
        return PS3000A_200MV;
      else if (range == 0.5)
        return PS3000A_500MV;
      else if (range == 1.0)
        return PS3000A_1V;
      else if (range == 2.0)
        return PS3000A_2V;
      else if (range == 5.0)
        return PS3000A_5V;
      else if (range == 10.0)
        return PS3000A_10V;
      else if (range == 20.0)
        return PS3000A_20V;
      else if (range == 50.0)
        return PS3000A_50V;
      else
      {
          std::ostringstream message;
          message << "Exception in " << __FILE__ << ":" << __LINE__ << ": Range value not supported: " << range;
          throw std::runtime_error(message.str());
      }
    }