## factorial

### Data

in lua

#### Tags

mathematics, recursion

### Source Code

``````-- Factorial algorithm implementation
-- See : http://en.wikipedia.org/wiki/Factorial

-- Recursive tail call implementation
local function factorial_recursive(n)
assert(n >= 0, ('Argument must be positive'))
if n == 0 then return 1 end
return n * factorial_recursive(n-1)
end

-- Iterative implementation
local function factorial_iterative(n)
local fact = 1
for i = 1, n do fact = fact * i end
return fact
end

return {
recursive = factorial_recursive,
iterative = factorial_iterative
}
``````
``````-- Tests for factorial.lua
local fact = require 'factorial'

local total, pass = 0, 0

local function dec(str, len)
return #str < len
and str .. (('.'):rep(len-#str))
or str:sub(1,len)
end

local function run(message, f)
total = total + 1
local ok, err = pcall(f)
if ok then pass = pass + 1 end
local status = ok and 'PASSED' or 'FAILED'
print(('%02d. %68s: %s'):format(total, dec(message,68), status))
end

run('Factorial.recursive should fail these tests', function()
assert(not pcall(fact.recursive))
assert(not pcall(fact.recursive, -1))
end)

run('Testing factorial.recursive', function()
assert(fact.recursive(0)  ==             1)
assert(fact.recursive(1)  ==             1)
assert(fact.recursive(5)  ==           120)
assert(fact.recursive(15) == 1307674368000)
end)

run('Factorial.iterative should fail these tests', function()
assert(not pcall(fact.iterative))
assert(not pcall(fact.iterative, -1))
end)

run('Testing factorial.iterative', function()
assert(fact.iterative(0)  ==             1)
assert(fact.iterative(1)  ==             1)
assert(fact.iterative(5)  ==           120)
assert(fact.iterative(15) == 1307674368000)
end)

print(('-'):rep(80))
print(('Total : %02d: Pass: %02d - Failed : %02d - Success: %.2f %%')
:format(total, pass, total-pass, (pass*100/total)))
``````