素朴挿入ソート

配列生成子を使ったものは、配列はみ出しの場合分けをしなくて済むが、死ぬほど遅いｗ　素朴な方がいい。

module m_isort2
    contains
    
    subroutine isort2( x )
      real, intent(in out) :: x(:)
      real :: tmp
      integer :: i, k, n
      n = size(x)
      if (n <= 1) return
      do k = n - 1, 1, -1
        tmp = x(k)
        do j = k + 1, n
          if ( tmp > x(j) ) then 
            x(j - 1) = x(j)
          else
            exit
          end if
        end do
        x(j - 1) = tmp
      end do
      return
    end subroutine isort2
  
    subroutine isort2x( x )
      real, intent(in out) :: x(:)
      real :: tmp
      integer :: i, k, n
      n = size(x)
      if (n <= 1) return
      do k = n - 1, 1, -1
        tmp = x(k)
        do j = k + 1, n
          if ( tmp < x(j) ) exit 
        end do
        x(k:) = [ x(k + 1:j - 1), tmp, x(j:) ] ! array constructor
      end do
      return
    end subroutine isort2x
  
  end module
 

  program sort2
    use m_isort2
    implicit none
    real, allocatable :: x(:)
    integer :: i 
    !
    allocate( x(10**5) )
    call random_seed()
    call random_number(x)
    call isort2x(x)
    print *, x
    do i = 1, size(x) - 1 ! check
      if (x(i) > x(i + 1) ) print *, 'error!', i
    end do
    stop
  end program sort2