# 1 "<stdin>"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "<stdin>"

module quantile_mod
! quantile finder. median = quantile( size(a)/2, a)
  implicit none
  contains
  recursive function quantile( k, a) result( value)
    integer, intent (in) :: k
    ! position in array
    real, dimension (:), intent (in) :: a
    real :: value
    ! output value of quantile
    integer :: j
    real :: ak
    ak = a( k)
    j = count( a < ak)
    ! how many a(:) < ak
    if ( j >= k) then
      value = quantile( k, pack( a, a < ak))
    else
      j = count( a > ak) + k - size( a)
      if ( j > 0) then
        value = quantile( j, pack( a, a > ak))
      else
        value = ak
      end if
    end if
  end function
end module