Determines the numeric value of a character as a decimal digit. If the
character is not a decimal digit according to GLib.ascii_isdigit,
-1 is returned.
Differs from GLib.unichar_digit_value because it takes a char, so
there's no worry about sign extension if characters are signed.
Parameters
c: number
an ASCII character
Returns number
the numerical value of c if it is a decimal digit, -1 otherwise
Determines the numeric value of a character as a decimal digit. If the character is not a decimal digit according to GLib.ascii_isdigit,
-1is returned.Differs from GLib.unichar_digit_value because it takes a char, so there's no worry about sign extension if characters are signed.