Validating and conversion of float

int main() {\n float f;\n cin >> f;\n if (!cin.fail()) {\n cout << f << endl;\n } else {\n cout << \"Invalid input\" << endl;\n }\n // your code goes here\n return 0;\n}\n\n\nThe fail() function checks the failbit and badbit on the stream. failbit signals what you want, if there was a logical error on I/O operation (example: try to read a float, but couldn't parse the token to a float) and badbit signals if there was a read/writing error on i/o operation (could not read/write token at all).",

When you use formatted reads combined with a check if everything is read you can determine if the [complete] value is a valid floating point number, e.g.:\n\nint main()\n{\n for (std::string test; std::cin >> test; ) {\n std::istringstream in(test);\n double value;\n if (in >> value >> std::ws && in.eof()) {\n std::cout << \"the string '\" << test << \"' is a valid floating point number\\n\";\n }\n else {\n std::cout << \"the string '\" << test << \"' is not a valid floating point number\\n\";\n }\n }\n}\n\n\nThe test does ignore whitespace surrounding the string. If that isn't desirable, the manipulator std::noskipws can be used and the use of std::ws can be omitted. Alternatively you can use strtod() do determine if the entire value represents a floating point number.\n\nWhat atof() is to simply see if the initial string of its argument is valid floating point number which is the case for the examples you quoted.",