JSON Library Tutorial from scratch (II): parsing digital learning and sorting notes

Original website ： From scratch JSON Library Tutorial - You know

JSON Number syntax

number = [ "-" ] int [ frac ] [ exp ]
int = "0" / digit1-9 *digit
frac = "." 1*digit
exp = ("e" / "E") ["-" / "+"] 1*digit

number Is expressed in decimal , It is mainly composed of 4 Part order consists of ： Minus sign 、 Integers 、 decimal 、 Index . Only integers are required . The difference between attention and intuition may be , A plus sign is illegal .

If the integer part is 0 Start , It can only be a single 0; And by the 1-9 At the beginning , You can add any number of numbers （0-9）. in other words ,0123 Not a legal one JSON Numbers .

The decimal part is more intuitive , Is one or more numbers after the decimal point （0-9）.

JSON Scientific notation can be used , The index part is capitalized E Or lowercase e Start , Then there can be a sign , Followed by one or more numbers （0-9）.

 C Library function - strtod()

C Library function  double strtod(const char *str, char **endptr)  Put parameters  str  The string pointed to is converted to a floating point number （ The type is double type ）. If  endptr  Not empty , The pointer to the character after the last character in the conversion will be stored in endptr The location of the reference .

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