/* *************** USAGE EXAMPLE *************** This code accepts unlimited samples of variable names to test, it will keep on working while input is non empty. REMEMBER! each sample in Code Playground input dialog needs to be separated by new line (←|) P.S. The 256 characters limit cannot be tested, because SoloLearn input is limited to 100 characters. Thank you : ) © 2017 SoloLearn Community ********************************************* https://www.sololearn.com/Discuss/889436/?ref=app CHALLENGE: The variable name is entered from the keyboard. Determine if it is correct from the point of view of C++? The variable name is entered from the keyboard. Determine if it is correct from the point of view of C++? The correct name of a variable can not begin with a digit, can not be longer than 256 characters, and does not contain special characters (except for '_') Code in C++ */ #include #include const char a = 'a'; const char A = 'A'; const char z = 'z'; const char Z = 'Z'; const char zero = '0'; const char nine = '9'; const char underscore = '_'; /* function validVarName Description: Process a string input and returns either one of the following value: 0 - It's a valid variable name 1 - Invalid, name is empty 2 - Invalid, name length exceeds 256 characters 3 - Invalid, name begins with a number 4 - Invalid, name contains unacceptable character(s) */ int validVarName(std::string vn) { if(vn.empty()) // Empty string return 1; size_t len = vn.length(); if(len > 256) // Exceeds 256 characters limit return 2; if(std::isdigit(vn[0])) // Begins with a number return 3; // The loop checks for invalid characters char ch; for(size_t i = 0; i < len; i++) { ch = vn[i]; if(ch < zero || ch > z) return 4; else { if(ch > nine && ch < A) return 4; if(ch > Z && ch < a) { if(ch != underscore) return 4; } } } return 0; } int main() { // Descriptive message for // validVarName return value std::string vnDesc[] = { "It's a valid variable name", "Invalid, it is empty", "Invalid, its length exceeds 256 characters", "Invalid, it begins with a number", "Invalid, it contains unacceptable character" }; std::string varname; int i {0}; do { std::getline(std::cin,varname); if(varname.empty()) break; std::cout << "Variable Name #" << ++i << "\n\"" << varname << "\"\n"; int rv = validVarName(varname); std::cout << vnDesc[rv] << "\n\n"; varname.clear(); } while (true); std::cout << std::endl; return 0; }

variable name validator