require 'facets/math/lngamma'

## This is the old definition by Josef Schugt.
##
## Around v2.0, Ruby finally added it's own `lgamma`
## function. That's good, but unforutnately it returns
## an array that includes the `sign(gamma(x))` too.
#
# def Math.lgamma(x)
#  h  = x + 5.5
#  h -= (x + 0.5) * log(h)
#
#  sum  =  1.000_000_000_190_015
#  sum += 76.180_091_729_471_46	     / (x + 1.0)
#  sum -= 86.505_320_329_416_77	     / (x + 2.0)
#  sum += 24.014_098_240_830_91	     / (x + 3.0)
#  sum -=  1.231_739_572_450_155	     / (x + 4.0)
#  sum +=  0.120_865_097_386_617_9e-2 / (x + 5.0)
#  sum -=  0.539_523_938_495_3e-5     / (x + 6.0)
#
#  -h + log(2.506_628_274_631_000_5 * sum / x)
# end