Determines the numeric value of a character as a decimal digit. Differs from g_unichar_digit_value() because it takes a char, so there's no worry about sign extension if characters are signed.
an ASCII character
If @c is a decimal digit (according to g_ascii_isdigit()), its numeric value. Otherwise, -1.
See Implementation
Determines the numeric value of a character as a decimal digit. Differs from g_unichar_digit_value() because it takes a char, so there's no worry about sign extension if characters are signed.