Automatic allocation of allocatable components of a type

forall
July 1, 2009 2:28 PM PDT
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#3 Reply to #1
This is correct and a feature of Fortran 2003.

Another related feature of Fortran 2003 is for allocatable arrays, where you could say:

integer, allocatable, dimension(:) :: a

a = [3,4,5]
and a would get automatically allocated to the proper shape, deallocating any previous allocation.  In Intel Fortran, this behavior is NOT the default and requires an option /assume:realloc_lhs.   However, the use you described with the derived type components does not require the option.

Steve,

While obviously convenient - is this also not a bit dangerous?

What happens if you erroneously do something like

a=[3,4,5]

...
a=[3,4,5,10]

where the use of a 4-element array is a bug (lets say due to bug)

Then my understanding is that F-2003 reallocates array a "behind your back", which would make it harder to catch this bug. Conversely F-95 would generate an access error and you'd have a pretty clear indication of a bug.

I suppose this comes down to safety vs convenience, I am not really criticizing, just contemplating ;-)

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