#include <iostream>
#include <string>

template <typename SubstringType>
bool substring_found(const std::string & String, const SubstringType & Substring)
{
    return String.find(Substring) != std::string::npos;
}
 
int main()
{
    std::string SomeString = "test";

    if (substring_found(SomeString, 'e'))
        std::cout << "substring 'e' found\n";

    if (!substring_found(SomeString, 'a'))
        std::cout << "no substring 'a' found\n";
}