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<a name="Character-Strings-in-Oct_002dFiles"></a>
<div class="header">
<p>
Next: <a href="Cell-Arrays-in-Oct_002dFiles.html#Cell-Arrays-in-Oct_002dFiles" accesskey="n" rel="next">Cell Arrays in Oct-Files</a>, Previous: <a href="Matrices-and-Arrays-in-Oct_002dFiles.html#Matrices-and-Arrays-in-Oct_002dFiles" accesskey="p" rel="prev">Matrices and Arrays in Oct-Files</a>, Up: <a href="Oct_002dFiles.html#Oct_002dFiles" accesskey="u" rel="up">Oct-Files</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Character-Strings-in-Oct_002dFiles-1"></a>
<h4 class="subsection">A.1.3 Character Strings in Oct-Files</h4>

<p>A character string in Octave is just a special <code>Array</code> class.
Consider the example:
</p>
<div class="example">
<pre class="verbatim">#include &lt;octave/oct.h&gt;

DEFUN_DLD (stringdemo, args, , &quot;String Demo&quot;)
{
  octave_value_list retval;
  int nargin = args.length ();

  if (nargin != 1)
    print_usage ();
  else
    {
      charMatrix ch = args(0).char_matrix_value ();

      if (! error_state)
        {
          retval(1) = octave_value (ch, '\'');  // Single Quote String

          octave_idx_type nr = ch.rows ();
          for (octave_idx_type i = 0; i &lt; 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, '&quot;');  // Double Quote String
        }
    }
  return retval;
}
</pre><pre class="example">

</pre></div>

<p>An example of the use of this function is
</p>
<div class="example">
<pre class="example">s0 = [&quot;First String&quot;; &quot;Second String&quot;];
[s1,s2] = stringdemo (s0)
&rArr; s1 = Second String
        First String

&rArr; s2 = First String
        Second String

typeinfo (s2)
&rArr; sq_string
typeinfo (s1)
&rArr; string
</pre></div>

<p>One additional complication of strings in Octave is the difference
between single quoted and double quoted strings.  To find out if an
<code>octave_value</code> contains a single or double quoted string use
one of the predicate tests shown below.
</p>
<div class="example">
<pre class="example">if (args(0).is_sq_string ())
  octave_stdout &lt;&lt; &quot;First argument is a single quoted string\n&quot;;
else if (args(0).is_dq_string ())
  octave_stdout &lt;&lt; &quot;First argument is a double quoted string\n&quot;;
</pre></div>

<p>Note, however, that both types of strings are represented by the
<code>charNDArray</code> type, and so when assigning to an
<code>octave_value</code>, the type of string should be specified.  For example:
</p>
<div class="example">
<pre class="example">octave_value_list retval;
charNDArray ch;
&hellip;
// 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, '&quot;');
</pre></div>

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<p>
Next: <a href="Cell-Arrays-in-Oct_002dFiles.html#Cell-Arrays-in-Oct_002dFiles" accesskey="n" rel="next">Cell Arrays in Oct-Files</a>, Previous: <a href="Matrices-and-Arrays-in-Oct_002dFiles.html#Matrices-and-Arrays-in-Oct_002dFiles" accesskey="p" rel="prev">Matrices and Arrays in Oct-Files</a>, Up: <a href="Oct_002dFiles.html#Oct_002dFiles" accesskey="u" rel="up">Oct-Files</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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