111 lines
3.4 KiB
Plaintext
111 lines
3.4 KiB
Plaintext
local fmt = require "fmt"
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local digitL <const> = {
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[" ## #"] = 0,
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[" ## #"] = 1,
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[" # ##"] = 2,
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[" #### #"] = 3,
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[" # ##"] = 4,
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[" ## #"] = 5,
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[" # ####"] = 6,
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[" ### ##"] = 7,
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[" ## ###"] = 8,
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[" # ##"] = 9
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}
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local digitR <const> = {
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["### # "] = 0,
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["## ## "] = 1,
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["## ## "] = 2,
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["# # "] = 3,
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["# ### "] = 4,
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["# ### "] = 5,
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["# # "] = 6,
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["# # "] = 7,
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["# # "] = 8,
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["### # "] = 9
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}
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local end_sentinel <const> = "# #" -- also at start
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local mid_sentinel <const> = " # # "
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local function decode_upc(s)
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local function decode_upc_impl(input)
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local upc = input:strip()
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if #upc != 95 then return false end
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local pos = 1
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local digits = {}
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local sum = 0
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local one_three = {1, 3}
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-- end sentinel
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if upc:sub(pos, pos + 2) == end_sentinel then
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pos += 3
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else
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return false
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end
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-- 6 left hand digits
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for _ = 1, 6 do
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local digit = digitL[upc:sub(pos, pos + 6)]
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if !digit then return false end
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digits:insert(digit)
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sum += digit * one_three[#digits % 2 + 1]
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pos += 7
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end
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-- mid sentinel
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if upc:sub(pos, pos + 4) == mid_sentinel then
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pos += 5
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else
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return false
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end
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-- 6 right hand digits
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for _ = 1, 6 do
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local digit = digitR[upc:sub(pos, pos + 6)]
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if !digit then return false end
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digits:insert(digit)
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sum += digit * one_three[#digits % 2 + 1]
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pos += 7
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end
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-- end sentinel
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if upc:sub(pos, pos + 2) != end_sentinel then return false end
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if sum % 10 == 0 then
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fmt.write("%s ", fmt.swrite(digits))
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return true
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end
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io.write("Failed Checksum ")
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return false
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end
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if decode_upc_impl(s) then
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print("Rightside Up")
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elseif decode_upc_impl(s:reverse()) then
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print("Upside Down")
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else
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print("Invalid digit(s)")
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end
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end
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local barcodes <const> = {
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" # # # ## # ## # ## ### ## ### ## #### # # # ## ## # # ## ## ### # ## ## ### # # # ",
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" # # # ## ## # #### # # ## # ## # ## # # # ### # ### ## ## ### # # ### ### # # # ",
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" # # # # # ### # # # # # # # # # # ## # ## # ## # ## # # #### ### ## # # ",
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" # # ## ## ## ## # # # # ### # ## ## # # # ## ## # ### ## ## # # #### ## # # # ",
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" # # ### ## # ## ## ### ## # ## # # ## # # ### # ## ## # # ### # ## ## # # # ",
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" # # # # ## ## # # # # ## ## # # # # # #### # ## # #### #### # # ## # #### # # ",
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" # # # ## ## # # ## ## # ### ## ## # # # # # # # # ### # # ### # # # # # ",
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" # # # # ## ## # # ## ## ### # # # # # ### ## ## ### ## ### ### ## # ## ### ## # # ",
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" # # ### ## ## # # #### # ## # #### # #### # # # # # ### # # ### # # # ### # # # ",
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" # # # #### ## # #### # # ## ## ### #### # # # # ### # ### ### # # ### # # # ### # # "
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}
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local n = 0
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for barcodes as barcode do
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++n
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fmt.write("%2d: ", n)
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decode_upc(barcode)
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end
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