Re: F90 derived type component as array

kus@xxxxxxxx wrote:
| Sorry,
|
| is there in F90 some restriction(s) for using of components (which are
| really arrays) of derived types
| instead of arrays itself ?
|
| I.e. if I have for example something like
|
| TYPE twoarray
| real, dimension (:,:) ::A
| real, dimension (:,:) ::B
| END TYPE twoarray
|
| TYPE(twoarray), DIMENSION(100) ::struct
|
| - may I use struct(k)%B in any place where I may use simple
| 2-dimensional array ?

Yes. However, your syntax is not correct; the arrays have to
be either fixed-shape:

TYPE twoarray
real, dimension (42,55) ::A
real, dimension (19,38) ::B
END TYPE twoarray

or have pointer attribute:

real, dimension (:,:), POINTER ::A
real, dimension (:,:), POINTER ::B

which you can later ALLOCATE, or, under Fortran2003/TR15581,
allocatable attribute:

real, dimension (:,:), ALLOCATABLE ::A
real, dimension (:,:), ALLOCATABLE ::B

Most modern compilers support that, so I suggest you try it first.

Additionally, you can also use e.g. struct(:)%B(23,37) to refer to
all B(23,37) members of all structs (if you ever need it),
but you cannot use struct(:)%B(:,:) to refer to all B's in all
structs.

| BTW, do I understand correctly that (in reality) memory requirements
| for twoarray structure are
| simple size(A)+size(B), i.e. "mapping" to the memory of this type is
| simple "memory for A" and
| then "memory for B" w/o any "control" information ?

In reality, yes, that's right. POINTER and ALLOCATABLE components
introduce a tiny overhead, in order of magnitude of 20 bytes per
dimension (compiler-dependent).

--
Jugoslav
___________
www.xeffort.com

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