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#!/usr/bin/env lua
--[[
Challenge 002
Challenge #2
Write a script that can convert integers to and from a base35
representation, using the characters 0-9 and A-Y. Dave Jacoby came up
with nice description about base35, in case you needed some background.
--]]
-- format a digit
function format_digit(n)
if n<10 then
return string.char(string.byte("0")+n)
else
return string.char(string.byte("A")+n-10)
end
end
-- format a number
function format_number(n, base)
local negative, output = false, ""
if n<0 then negative, n = true, math.abs(n); end
repeat
local d = n % base
n = math.floor(n / base)
output = format_digit(d)..output
until n==0
if negative then output = "-"..output; end
return output
end
-- main
if arg[1] == "-r" then
opt_r, n = true, arg[2]
else
opt_r, n = false, arg[1]
end
assert(n, "Usage: ch-2.lua [-r] nn")
if opt_r then
io.write(tonumber(n, 35), "\n")
else
io.write(format_number(tonumber(n), 35), "\n")
end
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