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fib.lua

 -- Copyright (c) 2008 the authors listed at the following URL, and/or
 -- the authors of referenced articles or incorporated external code:
 -- http://en.literateprograms.org/Fibonacci_numbers_(Lua)?action=history&offset=20081019232035
 -- 
 -- Permission is hereby granted, free of charge, to any person obtaining
 -- a copy of this software and associated documentation files (the
 -- "Software"), to deal in the Software without restriction, including
 -- without limitation the rights to use, copy, modify, merge, publish,
 -- distribute, sublicense, and/or sell copies of the Software, and to
 -- permit persons to whom the Software is furnished to do so, subject to
 -- the following conditions:
 -- 
 -- The above copyright notice and this permission notice shall be
 -- included in all copies or substantial portions of the Software.
 -- 
 -- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 -- EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 -- MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 -- IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 -- CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 -- TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 -- SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 -- 
 -- Retrieved from: http://en.literateprograms.org/Fibonacci_numbers_(Lua)?oldid=15146
 
 
 function fib(n) return n<2 and n or fib(n-1)+fib(n-2) end
 
 
 function fastfib(n)
 	fibs={[0]=0, 1, 1} -- global variable, outside the function
 
 	for i=3,n do
 		fibs[i]=fibs[i-1]+fibs[i-2]
 	end
 
 	return fibs[n]
 end
 
 
 metafib = { [0]=0, 1, 1 }
 local mt = {
 	__call = function(t, ...)
 		local args = {...}
 		local n = args[1]
 		
 		if not t[n] then
 			for i = 3, n do
 				t[i] = t[i-2] + t[i-1]
 			end
 		end
 
 		return t[n]
 	end
 }
 
 setmetatable(metafib, mt) -- now, metafib can be called as if it were a normal function
 
 
 for n=0,30 do print(fib(n)) end
 for n=0,30 do print(fastfib(n)) end
 for n=0,30 do print(metafib(n)) end