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arraysfortranvariable-declaration
Nordico
Nordico

Reputation: 1307

Array declaration in Fortran

Consider

INTEGER,DIMENSION(3) :: NumberVector

and

INTEGER              :: NumberVector(3)

Is there any difference whatsoever between these two declarations or are they exactly the same? (I mean in ANY possible context and variation: for example, in the case that those two were identical, what if I am declaring an array with an implicit size as one of the input parameter of a subroutine? Would it still be irrelevant which one I used?)

Upvotes: 6

Views: 1754

Answers (2)

Hristo Iliev
Hristo Iliev

Reputation: 74495

The DIMENSION attribute was added to Fortran 90 in order to improve code clarity and to enable code savings when declaring multiple arrays of the same type (not uncommon in scientific computing), e.g. instead of

REAL :: mat1(10,20), mat2(10,20), mat3(10,20), mat4(10,20), mat5(10,20)

one could write

REAL, DIMENSION(10,20) :: mat1, mat2, mat3, mat4, mat5

Besides reducing source code size and compilation time (less parsing; not that relevant nowadays), this reduces the possibility of making a mistake in any of the declarations. Otherwise both forms are equal and the variables declared behave exactly the same way everywhere in the program.

Upvotes: 3

Vladimir F Героям слава
Vladimir F Героям слава

Reputation: 60123

Yes, it is identical. Even for assumed, deferred and whatever possible shape.

Upvotes: 8

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