><tbody><tr><td><span class="term"><i><tt>ctxt</tt></i>:</span></td><td>the expression context</td></tr><tr><td><span class="term"><i><tt>exp</tt></i>:</span></td><td>the expression</td></tr><tr><td><span class="term"><i><tt>str</tt></i>:</span></td><td>the string</td></tr><tr><td><span class="term"><i><tt>len</tt></i>:</span></td><td>the string len in bytes if available</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>the resulting expression or NULL in case of internal error</td