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<a name="Character-Strings-in-Oct_002dFiles"></a>
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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> [<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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<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 <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;
}
</pre></div>
<p>An example of the use of this function is
</p>
<div class="example">
<pre class="example">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
</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 << "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";
</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;
…
// 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, '"');
</pre></div>
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