可分配的陣列

陣列可以具有可分配的屬性:

! One dimensional allocatable array
integer, dimension(:), allocatable::foo
! Two dimensional allocatable array
real, dimension(:,:), allocatable::bar

這宣告瞭變數,但沒有為它分配任何空間。

! 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

一旦不再需要變數,就可以取消分配

deallocate(foo)

如果由於某種原因 allocate 語句失敗,程式將停止。如果通過 stat 關鍵字檢查狀態,則可以防止這種情況:

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

deallocate 語句也有 stat 關鍵字:

deallocate (geese, stat=status)

status 是一個整數變數,如果分配或取消分配成功,則其值為 0。