string C; cin>>C; if (C=="add" ){ int a=add(A,B); cout<<a<<endl; I have here a simple condition where i am taking input "C" to ask the user to write which math operation they want to run. The user might input in capital letters or the first letter might be uppercase and the rest be lowercase. What should I do so that the program reads all the inputs weather uppercase or lowercase as the same?
Transform the user input into all lowercase or uppercase.
#include <algorithm> #include <cctype> #include <string> std::string toLowerCase(const std::string& str) { std::string lower(str); std::transform(lower.begin(), lower.end(), lower.begin(), ::tolower); return lower; } 
-1 to an unsigned integer is well defined in C++: it produces a value with all bits set. Thus, static_cast<unsigned char>(-1) is just 255 (assuming unsigned char is 8-bit, which is typically the case). And then, since 255 is "representable as unsigned char" (because we've just converted it by casting), I don't see UB here.unsigned char gives it a different meaning. And unless tolower maps 255 to a value between 0 and 127, the effect of casting the result of tolower(255) to char is implementation defined. So you really can't count on anything.