! Copyright 2005-2017 ECMWF.
!
! This software is licensed under the terms of the Apache Licence Version 2.0
! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
! 
! In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
! virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
!
!
!  Description: how to use an iterator on lat/lon/values.
!
!
program iterator
use grib_api
implicit none
  integer            :: ifile
  integer            :: iret,iter
  real(kind=8)       :: lat,lon,value,missingValue
  integer            :: n,flags
  character(len=256) :: filename
  character(len=256) :: error

!     Message identifier.
  integer            :: igrib

  ifile=5

  call grib_open_file(ifile, &
       '../../data/regular_latlon_surface_constant.grib1','R')

! Loop on all the messages in a file.

  call grib_new_from_file(ifile,igrib,iret)

  LOOP: DO WHILE (iret/=GRIB_END_OF_FILE)
! get as a real8
      call grib_get(igrib, &
           'missingValue',missingValue)
      write(*,*) 'missingValue=',missingValue

! A new iterator on lat/lon/values is created from the message igrib
      flags = 0
      call grib_iterator_new(igrib,iter,flags)

      n = 0
! Loop on all the lat/lon/values.
      call grib_iterator_next(iter,lat,lon,value, iret)
      do while (iret .ne. 0)
! You can now print lat and lon,
         if ( value .eq. missingValue ) then
! decide what to print if a missing value is found.
           write(*,*) "- ",n," - lat=",lat," lon=",lon," value=missing"
         else
! or print the value if is not missing.
           write(*,*) " ",n," lat=",lat," lon=",lon," value=",value
         endif

         n=n+1

         call grib_iterator_next(iter,lat,lon,value, iret)
      end do

! At the end the iterator is deleted to free memory.
  call grib_iterator_delete(iter)
  call grib_release(igrib)

  call grib_new_from_file(ifile,igrib, iret)

  end do LOOP


  call grib_close_file(ifile)

  end program iterator
