CHAR<
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Syntax: (char< {<character> ...})
This function compares the given characters in the
same way like numbers.
The following ordering on characters exists:
A < ... < Z
a < ... < z
0 < ... < 9
The ordering between those groups is unspecified and
depends on the implementation. But most of the time
the characters are in the ASCII ordering.
0...9 < A...Z < a...z.
It returns T, when the ordering is given, otherwise
NIL.
example: >(char< #\a #\b)
T