The `ord()` function extracts the byte value of the character within the
given input string at the given offset.

If the offset argument is omitted, the byte value of the first character
is returned.

Returns `null` if the given input string argument is not a string.

Returns `null` if the given input string is empty.

Returns `null` if the given offset value is invalid.

Invalid offsets are non-integer values or integers equal to or larger than
the length of the input string. Negative offsets are converted to positive
ones by adding the length of the input string. If the negative value is
too large, the offset is considered invalid.


-- Testcase --
{%
	print(join("\n", [
		ord(123),
		ord(""),
		ord("abcd", "inval"),
		ord("abcd"),
		ord("abcd", 0),
		ord("abcd", 1),
		ord("abcd", -1),
		ord("abcd", 10),
		ord("abcd", -10)
	]), "\n");
%}
-- End --

-- Expect stdout --
null
null
null
97
97
98
100
null
null
-- End --