# cusip.icn -- Committee on Uniform Security Identification Procedures

procedure main()
   local code, codes
   codes := ["037833100", "17275R102", "38259P508",
            "594918104", "68389X106", "68389X105"]
   while code := pop(codes) do {
      writes(code, " : ")
      if check_code(code) then
         write("valid.")
      else write("not valid.")
      }
end

procedure check_code(c)
   local p, sum, value
   static codetable
   initial codetable := buildtable()

   sum   := 0
   value := 0
   every p := 1 to 8 do {
      if p % 2 = 1 then    # odd position
         value := codetable[c[p]]
      else                 # even position
         value := 2 * codetable[c[p]]
      sum +:= (value / 10) + (value % 10)
      }
   sum := (10 - (sum % 10)) % 10
   if sum = c[9] then return else fail
end

procedure buildtable()
   local chars, n, t
   t := table()
   chars := &digits || &ucase || "*@#"
   every n := 1 to *chars do
      t[chars[n]] := (n - 1)
   return t
end