Re: Convert double to octave_value for assignment to column vector

[babelproofreader]

I still can't get this to work. My code now, heavily commented, is

#include <octave/oct.h>
#include <octave/dColVector.h>
#include <octave/parse.h> // necessary for the call to feval
#include <octave/ov.h> // necessary for conversion to double

DEFUN_DLD (rm_compile_1, args, , "Input is a column vector, output is median
vector. This is a test of compiling Octave median function")
{
octave_value_list retval;

 ColumnVector rm_compile_1_input = args(0).column_vector_value (); // input
vector
 ColumnVector rm_compile_1_output = args(0).column_vector_value (); // copy
of input vector to hold median of input vector as an output vector
 octave_value input_median; // declare an octave value to hold output of
feval call to Octave median function 
 double double_input_median; // declare a double value to hold conversion of
octave_value feval call to a double
 // *** octave_value_list my_retval; // declare an octave value to hold
conversion of loop output vector for passing as return value "retval"

 input_median = feval ( "median", octave_value (rm_compile_1_input) ); //
call Octave's median function with "feval"
 double_input_median = input_median.double_value (); // convert "feval"
output to double value for assignment to output column_vector 

 for (octave_idx_type ii (0); ii < args(0).length (); ii++) // loop to fill
output column_vector with converted-to-double median value
     {
     rm_compile_1_output(ii) = double_input_median;
     }

// *** my_retval = octave_value (rm_compile_1_output); // convert loop
output to an octave value for passing to retval
// *** retval = my_retval;
retval = rm_compile_1_output;

return retval;
}

which fails with cc:26: error: no match for ‘operator=’ in ‘retval =
rm_compile_1_output’ and I don't understand why this should be so.

An alternative version is to uncomment the lines // *** and use my_retval as
retval, which does compile without error, but when the function is called it
produces 
error: octave_base_value::double_value (): wrong type argument `list'

I am really at a loss to understand why, after converting input_median to a
double and assigning it to the output column_vector in the loop, that this
loop output does not seem to be recognised. 
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