checking for user input that isn't a number

I'm wondering if there is a way to check that user input entered via a console-based C++ application is not a number. I suppose one algorithm is to break up the user-entered data character by character and check that each character is 0,1,2...9 or a decimal point. But maybe there is some class that already has this functionality that I'm missing, or a way that involves less brute force and more elegance? Thanks.