Re: Changing data type in octave_value_list

[Søren Hauberg]

Hi,
  I'm not exactly sure if the following solve your problem, but it's
worth a shot:

  #include <octave/oct.h>
  #include <cstdlib>
  
  DEFUN_DLD(bla, args, nargout, "...")
  {
    if (args(0).is_string()) {
       args(0) = octave_value( atof(args(0).string_value().c_str()) );
    }
    return args;
  }

I didn't have convert_s2i, so I converted to a double instead. The real
change is the use of the 'octave_value' constructor. Basicly you have to
insert 'octave_value's in an octave_value_list.

Hope it helps,
Søren

fre, 11 08 2006 kl. 12:52 -0600, skrev Joshua Rigler:
> This might be more of a C/C++ question, so please be kind...
> 
> I am writing a .oct file, and the source includes the following standard 
> definition at the beginning:
> 
>    DEFUN_DLD (cdflib, args, nargout, "...whatever...")
> 
> As I understand things, 'args' is my input list, passed from the 
> interpreter, and of type octave_value_list.  I want to be able to pass 
> one of my inputs as either a scalar, or a string that I can then 
> convert/map to a corresponding scalar and place back into the same 
> position in args, before proceeding to subsequent operations.
> 
> What I naively thought I could do is (paraphrased):
> 
>    if (args(0).is_string)
>    {
>      args(0) = double (convert_s2i(args(0).string_value) );
>    }
> 
> ...where 'convert_s2i' is just a function that maps certain strings to 
> long integers, which I am then happy to store as double-floats, since 
> this is what Octave expects (I suppose newer versions have support for 
> additional data types, including integers, but I'm perfectly happy with 
> doubles).  Note, I am not simply trying to convert an ascii '1' into its 
> scalar equivalent, but rather a multi-character string that associates 
> with a particular integer inside a C++ map object.
> 
> Anyway, the problem I face is that I keep getting the following error:
> 
>    error: invalid conversion from string to real scalar
> 
> I assume this corresponds to my attempt to transform args(0) from a 
> string into a scalar.  Is there a straight-forward way to do this?
> Thanks.
> 
> -EJR
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