Next: Cell Arrays in Oct-Files, Previous: Matrices and Arrays in Oct-Files, Up: Oct-Files [Contents][Index]
A character string in Octave is just a special Array
class. Consider
the example:
#include <octave/oct.h> DEFUN_DLD (stringdemo, args, , "String Demo") { if (args.length () != 1) print_usage (); octave_value_list retval; charMatrix ch = args(0).char_matrix_value (); retval(1) = octave_value (ch, '\''); // Single Quote String 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, '"'); // Double Quote String 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 use one of the predicate tests shown
below.
if (args(0).is_sq_string ()) octave_stdout << "First argument is a single quoted string\n"; else if (args(0).is_dq_string ()) octave_stdout << "First argument is a double 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 ch; … // Create single quoted string retval(1) = octave_value (ch); // default constructor is sq_string OR retval(1) = octave_value (ch, '\''); // explicitly create sq_string // Create a double quoted string retval(0) = octave_value (ch, '"');