trimming \n \t from xmlChar not working

trimming \n \t from xmlChar not working

#include "boost/algorithm/string/trim.hpp"
..
..
xmlChar *v = NULL;
cur = xmlDocGetRootElement(doc);
for (cur = cur->xmlChildrenNode; cur != NULL; cur = cur->next) {
v = xmlGetProp(cur, (const xmlChar *)"value");
trim((char*)v);
printf("%s",v);
}
This code doesn't compile, says trim is not defined, I tried boost::trim
and it did not help. thanks.