Re: value extractors for octave_value class

[John W. Eaton]

On 11/11/2015 11:21 PM, Jordi Gutiérrez Hermoso wrote:
> On Wed, 2015-11-11 at 11:59 -0500, John W. Eaton wrote:
>
> > When overloading these functions with (for example)
> >
> >     Array<double> vector_value (const char *fmt, ...) const;
> >
> > some compilers complained that the overloaded function was ambiguous.
> > I'm not sure what is best here.
>
> How about just overloading with std::string arguments and requiring
> the function caller to use sprintf in case they need formatting?
>
> So, for example,
>
>     auto x = foo.int_value(sprintf("error: want %s but got %s", bar, baz))

I don't think we should be using "auto" in Octave code just yet.

Some reasons to not do this are that sprintf requires a buffer to be 
allocated, so that would complicate things and the sprintf operation and 
the std::string object creation would happen on each call even if they 
are never needed.  With the fmt+varargs approach, the arguments just 
need to be passed (as pointers) and if the error doesn't happen, then 
the formatting doesn't have to be done.

jwe