test_indnth Subroutine

subroutine test_indnth
use M_orderpack__indnth, only : indnth
implicit none
integer,allocatable :: iarr(:)
integer :: i
integer :: imiddle
   call unit_check_start('indnth', '-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 minloc() and maxloc()
   call unit_check('indnth',all(indnth(iarr,1         ).eq.minloc(iarr)),'like minloc()')
   call unit_check('indnth',all(indnth(iarr,size(iarr)).eq.maxloc(iarr)),'like maxloc()')

   ! but more generally it can return the Nth lowest value.
   call unit_check('indnth',iarr(indnth(iarr,8)).eq.80,'Nth value')
   ! so a value at the middle would be
   imiddle=(size(iarr)+1)/2
   call unit_check('indnth',iarr(indnth(iarr,imiddle)).eq.40,'find median')
   ! sort the hard way, one value at a time
   call unit_check('indnth', all([(iarr(indnth(iarr,i)),i=1,size(iarr))].eq.[10,20,30,40,50,60,70,80]),'sort hard way')

   call unit_check_done('indnth',msg='test completed')
end subroutine test_indnth