[mod-security-users] string compare

[<877...@qq...>]

hi all, 


Who can help me understand why the highlighted is not  toupper(aa) == toupper(bb)  or tolower(aa)==tolower(bb)  ?


in file ModSecurity/src/variables/variable.h


class VariableMonkeyResolution {
 public:
    VariableMonkeyResolution () { } 
    static inline bool comp(const std::string &a, const std::string &b) {
        return a.size() == b.size()
             && std::equal(a.begin(), a.end(), b.begin(),
            [](char aa, char bb) {
            return toupper(aa) == bb; 
        }); 
    }   



thanks
huiming