# NOT RUN {
#
# Show all possible input values:
#
a()
#
# Convert them in one letter-code:
#
aaa(a())
#
# Check consistency of results:
#
stopifnot(a(aaa(a())) == a())
#
# Show what happens with non-allowed values:
#
aaa("Z") # should be NA and a warning is generated
# }
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