C++ Namespace and transform

We are migrating from an older intel compiler (version 11) to version 15 and getting this namespace error.

Trying to find inof on why the transform throwing an error

Thoughts ?

Thanks

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Error:

main.cc(16): error: namespace "std" has no member "transform  

std::transform(strToConvert.begin(), strToConvert.end(), strToConvert.begin(), ::toupper);

Code:

#include <stdio.h>
#include <iostream>
#include <cctype>
#include <clocale>
#include <string>

using namespace std;

main() {

string strToConvert;

strToConvert="Hello Alan";

    std::transform(strToConvert.begin(), strToConvert.end(), strToConvert.begin(), ::toupper);

}