In Octave a character string is just a special Array class.
Consider the example:
#include <octave/oct.h>
DEFUN_DLD (stringdemo, args, , "String Demo")
{
int nargin = args.length();
octave_value_list retval;
if (nargin != 1)
print_usage ();
else
{
charMatrix ch = args(0).char_matrix_value ();
if (! error_state)
{
if (args(0).is_sq_string ())
retval(1) = octave_value (ch, true);
else
retval(1) = octave_value (ch, true, '\'');
octave_idx_type nr = ch.rows();
for (octave_idx_type i = 0; i < nr / 2; i++)
{
std::string tmp = ch.row_as_string (i);
ch.insert (ch.row_as_string(nr-i-1).c_str(),
i, 0);
ch.insert (tmp.c_str(), nr-i-1, 0);
}
retval(0) = octave_value (ch, true);
}
}
return retval;
}
An example of the use of this function is
s0 = ["First String"; "Second String"];
[s1,s2] = stringdemo (s0)
⇒ s1 = Second String
First String
⇒ s2 = First String
Second String
typeinfo (s2)
⇒ sq_string
typeinfo (s1)
⇒ string
One additional complication of strings in Octave is the difference
between single quoted and double quoted strings. To find out if an
octave_value contains a single or double quoted string an example is
if (args(0).is_sq_string ())
octave_stdout <<
"First argument is a singularly quoted string\n";
else if (args(0).is_dq_string ())
octave_stdout <<
"First argument is a doubly quoted string\n";
Note however, that both types of strings are represented by the
charNDArray type, and so when assigning to an
octave_value, the type of string should be specified. For example:
octave_value_list retval;
charNDArray c;
...
// Create single quoted string
retval(1) = octave_value (ch, true, '\'');
// Create a double quoted string
retval(0) = octave_value (ch, true);