The function converts the string s into a double number. Normally, the base is decimal and must have the following format:[Blank space] [Sign] [Digits] [.Digits] [ [Sign]Digits]String parsing ceases at the first non-compliant character.If the string cannot be converted into a number, 0.0 is returned.If the string starts with 0x, the base used is 16. Only integer numbers can be read in.