Floating point constants have the following format:
Sign (optional) – either plus (+) or minus (–)
Integer (optional) – zero or more decimal digits (0–9)
Fraction (optional) – decimal point (.) followed by zero or more decimal digits
Exponent (optional) – the letter “e” or “E”, followed by an optional sign (plus or minus), followed by one or more decimal digits (0–9)
A valid floating point constant must have either an integer part or a fractional part.