DATA:
# IN:
digit?.in is text   # char

# OUT:
digit?    is number # bool

# LOCALS:
digit?.digits is number vector

PROCEDURE:
store 1 in digit?.digits:"0"
store 1 in digit?.digits:"1"
store 1 in digit?.digits:"2"
store 1 in digit?.digits:"3"
store 1 in digit?.digits:"4"
store 1 in digit?.digits:"5"
store 1 in digit?.digits:"6"
store 1 in digit?.digits:"7"
store 1 in digit?.digits:"8"
store 1 in digit?.digits:"9"

# Test if character is a single digit number or not.
#  IN: digit?.in
# OUT: digit?
sub-procedure digit?
    store digit?.digits:digit?.in in digit?
end sub-procedure