Example
Arrays can have the allocatable attribute:
! One dimensional allocatable array
integer, dimension(:), allocatable :: foo
! Two dimensional allocatable array
real, dimension(:,:), allocatable :: bar
This declares the variable but does not allocate any space for it.
! We can specify the bounds as usual
allocate(foo(3:5))
! It is an error to allocate an array twice
! so check it has not been allocated first
if (.not. allocated(foo)) then
allocate(bar(10, 2))
end if
Once a variable is no longer needed, it can be deallocated:
deallocate(foo)
If for some reason an allocate statement fails, the program will stop. This can be prevented if the status is checked via the stat keyword:
real, dimension(:), allocatable :: geese
integer :: status
allocate(geese(17), stat=status)
if (stat /= 0) then
print*, "Something went wrong trying to allocate 'geese'"
stop 1
end if
The deallocate statement has stat keyword too:
deallocate (geese, stat=status)
status is an integer variable whose value is 0 if the allocation or deallocation was successful.
