C/C++ counting the number of decimals?

Question

Lets say that input from the user is a decimal number, ex. 5.2155 (having 4 decimal digits). It can be stored freely (int,double) etc.

Is there any

Answer 1

Years after the fight but as I have made my own solution in three lines :

string number = "543.014";    
size_t dotFound;
stoi(number, &dotFound));
string(number).substr(dotFound).size()

Of course you have to test before if it is really a float (With stof(number) == stoi(number) for example)