test_fndnth Subroutine

subroutine test_fndnth
use M_orderpack__fndnth, only : fndnth
implicit none
integer,allocatable :: iarr(:)
integer :: i
integer :: imiddle
   call unit_check_start('fndnth', '-library orderpack') ! start tests
   ! find Nth lowest value in an array without sorting entire array
   iarr=[80,70,30,40,50,60,20,10]
   ! can return the same values as intrinsics minval() and maxval()
   call unit_check('fndnth',fndnth(iarr,1).eq.minval(iarr),'like minval()')
   call unit_check('fndnth',fndnth(iarr,size(iarr)).eq.maxval(iarr),'like maxval()')
   ! but more generally it can return the Nth lowest value.
   call unit_check('fndnth',fndnth(iarr,8).eq.80,'Nth value')
   ! so a value at the middle would be
   imiddle=(size(iarr)+1)/2
   call unit_check('fndnth',fndnth(iarr,imiddle).eq.40,'find median')
   ! sort the hard way, one value at a time
   call unit_check('fndnth', all([(fndnth(iarr,i),i=1,size(iarr))].eq.[10,20,30,40,50,60,70,80]),'sort hard way')
   call unit_check_done('fndnth',msg='test completed')
end subroutine test_fndnth