The QDoubleValidator class provides range checking of floating-point numbers. ... QDoubleValidator  ( double bottom, double top, int decimals, QWidget * parent, const char * name = 0 )  . ... Creates a validator object which accepts all double from 2.7182818 to 3.1415926 (please, no bug reports) with at most seven digits after the decimal point. ... Creates a validator object which accepts all doubles from bottom up to and including top with at most decimals digits after the decimal point. ...