57 lines
1.7 KiB
Text
57 lines
1.7 KiB
Text
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local fmt = require "fmt"
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local d = {
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{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
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{1, 2, 3, 4, 0, 6, 7, 8, 9, 5},
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{2, 3, 4, 0, 1, 7, 8, 9, 5, 6},
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{3, 4, 0, 1, 2, 8, 9, 5, 6, 7},
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{4, 0, 1, 2, 3, 9, 5, 6, 7, 8},
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{5, 9, 8, 7, 6, 0, 4, 3, 2, 1},
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{6, 5, 9, 8, 7, 1, 0, 4, 3, 2},
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{7, 6, 5, 9, 8, 2, 1, 0, 4, 3},
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{8, 7, 6, 5, 9, 3, 2, 1, 0, 4},
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{9, 8, 7, 6, 5, 4, 3, 2, 1, 0}
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}
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local inv = {0, 4, 3, 2, 1, 5, 6, 7, 8, 9}
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local p = {
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{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
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{1, 5, 7, 6, 2, 8, 3, 0, 9, 4},
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{5, 8, 0, 3, 7, 9, 6, 1, 4, 2},
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{8, 9, 1, 6, 0, 4, 3, 5, 2, 7},
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{9, 4, 5, 3, 1, 2, 6, 8, 7, 0},
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{4, 2, 8, 6, 5, 7, 3, 9, 0, 1},
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{2, 7, 9, 3, 8, 0, 6, 4, 1, 5},
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{7, 0, 4, 6, 9, 1, 3, 2, 5, 8}
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}
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local function verhoeff(s, validate, table)
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if table then
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print($"{validate ? "Validation" : "Check digit"} calculations for '{s}':\n")
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print(" i nᵢ p[i,nᵢ] c")
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print("------------------")
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end
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if !validate then s ..= "0" end
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local c = 0
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local le = #s - 1
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for i = le, 0, -1 do
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local ni = s[i + 1]:byte() - 48
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local pi = p[(le - i) % 8 + 1][ni + 1]
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c = d[c + 1][pi + 1]
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if table then fmt.print("%2d %d %d %d", le - i, ni, pi, c) end
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end
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if table and !validate then print($"\ninv[{c + 1}] = {inv[c + 1]}") end
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return !validate ? inv[c + 1] : c == 0
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end
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local sts = {{"236", true}, {"12345", true}, {"123456789012", false}}
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for sts as st do
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local c = verhoeff(st[1], false, st[2])
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print($"\nThe check digit for '{st[1]}' is '{c}'\n")
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for {st[1] .. tostring(c), st[1] .. "9"} as stc do
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local v = verhoeff(stc, true, st[2])
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print($"\nThe validation for '{stc}' is {v ? "correct" : "incorrect"}.\n")
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end
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end
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