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<h4 class="subsection" id="Character-Strings-in-Mex_002dFiles-1"><span>A.2.3 Character Strings in Mex-Files<a class="copiable-link" href="#Character-Strings-in-Mex_002dFiles-1"> ¶</a></span></h4>
<p>As mex-files do not make the distinction between single and double quoted
strings that Octave does, there is perhaps less complexity in the use of
strings and character matrices. An example of their use that parallels the
demo in <samp class="file">stringdemo.cc</samp> is given in the file <samp class="file">mystring.c</samp>, as shown
below.
</p>
<div class="example smallexample">
<pre class="verbatim">#include <string.h>
#include "mex.h"
void
mexFunction (int nlhs, mxArray *plhs[],
int nrhs, const mxArray *prhs[])
{
mwSize m, n;
mwIndex i, j;
mxChar *pi, *po;
if (nrhs != 1 || ! mxIsChar (prhs[0])
|| mxGetNumberOfDimensions (prhs[0]) > 2)
mexErrMsgTxt ("ARG1 must be a char matrix");
m = mxGetM (prhs[0]);
n = mxGetN (prhs[0]);
pi = mxGetChars (prhs[0]);
plhs[0] = mxCreateNumericMatrix (m, n, mxCHAR_CLASS, mxREAL);
po = mxGetChars (plhs[0]);
for (j = 0; j < n; j++)
for (i = 0; i < m; i++)
po[j*m + m - 1 - i] = pi[j*m + i];
}
</pre></div>
<p>An example of its expected output is
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">mystring (["First String"; "Second String"])
⇒ Second String
First String
</pre></div></div>
<p>Other functions in the mex interface for handling character strings are
<code class="code">mxCreateString</code>, <code class="code">mxArrayToString</code>, and
<code class="code">mxCreateCharMatrixFromStrings</code>. In a mex-file, a character string is
considered to be a vector rather than a matrix. This is perhaps an arbitrary
distinction as the data in the <code class="code">mxArray</code> for the matrix is consecutive in
any case.
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