Re: error function

[Shai Ayal]

On 5/15/07, John W. Eaton <address@hidden> wrote:
> On 15-May-2007, Shai Ayal wrote:
>
> | This is of course recoverable. How about using the approach taken by
> | octave_value when trying to extract a wrong type? The following code
> | is used in many places:
> |
> | void somefunc ( octave_value& val)
> |       std::string c = val.string_value ();
> |
> |       if (! error_state )
> |
> | does octave_value set the error_state directly or does it call a function?
>
> The string_value method calls error if it can't perform the
> conversion.

but no error messge is printed right? does it call error ("") ?

> | When the value is "none", then the relevant element shouldn't be drawn
> | at all -- an eample is line.markeredgecolor which can be none and than
> | the markers will ot have the edge drawn, only the face.
> | The "auto" value is a bit contrived -- an example doesn't spring to
> | mind, but it is conceiveable that then the color would have to be
> | computed based on the value of other properties as well, so it can't
> | be computed by the rgb function.
>
> Maybe you need
>
>  bool rgb_property::is_none (void) const;
>  bool rgb_property::is_auto (void) const;
>  const double *rgb_property::rgb_value (void) const;
>
> and then code that uses this class will just have to check if it cares
> about "none" and "auto".  I don't know what else to suggest unless the
> rgb function can somehow return reasonable values when the state is
> "none" or "auto".

I thought of is_rgb and is_radio. However I recal thatusing is_*
functions was the way to determine octave_value type, but then I read
somewhere that the recomended way was to try and convert and than
check error_state, as above. Can you elaborate on why this is
recommended for octave_value?

> jwe