Re: Checking octave_value equality (==) without generating an error?

[Daniel J Sebald]

On 11/22/2014 04:17 PM, Michael Goffioul wrote:
> On Sat, Nov 22, 2014 at 4:45 PM, Daniel J Sebald <address@hidden
> <mailto:address@hidden>> wrote:
>
>     Try "try".
>
>
> Not sure I'm following... I was referring to a method/function in C++.

Ah...  Well, there is such an animal in C++, as you've explored, but it 
does apparently take more work to define exactly what the exception is.


> Even something like the following will print an error message at octave
> prompt:
>
> bool result;
> // Assign ov1 and ov2 such that they're not comparable ({} == false)
> octave_value ov1 (Cell ());
> octave_value ov2 (false);
> try
> {
>    result = (ov1 == ov2);
> }
> catch (...)
> {
>    result = false;
> }
>
> However, now that I'm thinking about it, what I'm looking for is
> something along those lines:
>
> bool is_equal_safe (const octave_value& ov1, const octave_value& ov2)
> {
>    bool retval;
>    unwind_protect frame;
>
>    frame.protect_var (error_state);
>    frame.protect_var (warning_state);
>    frame.protect_var (discard_error_messages);
>    frame.protect_var (warning_error_messages);
>
>    discard_error_messages = true;
>    discard_warning_messages = true;
>
>    try
>    {
>      octave_value ov_cmp_retval = (ov1 == ov2);
>      retval = ov_cmp_retval.bool_value ();
>    }
>    catch (octave_execution_exception)
>    {
>      retval = false;
>    }
>
>    return retval;
> }
>
> But this looks a bit overkill if something similar already exists in
> octave code base.

John's the best reference on that one.

It's not that bad, though, as far as code.  It looks like the overkill 
part is having to set up the environment to prevent Octave warnings from 
happening.  If nothing exists, then if it can be written as a macro to 
replace "(ov1 == ov2)" with any general expression, that might be nice.

Dan