Function prototype to parse base-10 integers and floating point values.

You can find more information in comments below.

/**
    Function prototype which try to parse float and integer value. If succeeded, set index to next character and store found value in result 
    @param options Parser setting 
    @param s String where to search/parse 
    @param min Minimum index in string for looking up(in general) 
    @param max Maximum index in string for looking up(in general) 
    @param index [in, out] Index in string at which check if it is float number. On success updated to the index right after number end 
    @param is_int [out] Whether result is integer or float 
    @param i [out] Integer result if is_int is true 
    @param f [out] Float result if is_int is false 
    @return true if there is number at specified index 
    */
    using FParseNumber = bool(*)(const PARSER_OPTIONS &options, FGetChar get, const String &s, const int min, const int max, int &index, bool &is_int, long long &i, double &f);