The numeric code for a given character
This function maps a character to its code, for example: (char-code #\A) evaluates to 65. See code-char for a sort of inverse function, which maps a code to the corresponding character.
Completion Axiom (completion-of-char-code):
(equal (char-code x) (if (characterp x) (char-code x) 0))
Guard for (char-code x):
(characterp x)
This function maps all non-characters to 0.
