character array allocation, alternative definition fails

[Johannes_Rieke]

Hi all,

here the basics of allocated characters are discussed:

https://software.intel.com/en-us/forums/intel-visual-fortran-compiler-for-windows/topic/287349

Now I have the following minimal working example:

!
program character_array_allocation
  implicit none
  ! Variables
  character(len=:),dimension(:), allocatable :: foo
  
  allocate(character(len=10),dimension(20) :: foo) ! this fails
! 1>------ Build started: Project: character_array_allocation, Configuration: Debug Win32 ------
! 1>Compiling with Intel(R) Visual Fortran Compiler 17.0.1.143 [IA-32]...
! 1>character_array_allocation.f90
! 1>... \character_array_allocation.f90(7): error #5082: Syntax error, found ',' when expecting one of: . , [ % . ( :: )
! 1>compilation aborted for ... \character_array_allocation.f90 (code 1)
  
  
  !allocate(character(len=10) :: foo(20)) ! this works
  

end program character_array_allocation

Why causes the alternative format in line 7 a compiler error? The version in line 15 works fine.

Thanks, Johannes

[Arjen_Markus]

I do not think the syntax that is failing is valid Fortran. At the very least I do not remember seeing that.

[Johannes_Rieke]

Hi Arjen,

thanks for your answer. My thought was, if the definition in line 5 is valid, why should it not be valid in the allocation. Sounded logically for me, but maybe isn't. gfortran (4.8.x) does not accept line 7 also.

[Arjen_Markus]

Yes, that might have been logical, indeed. I do not know why it should not be, but the type clause "character(len=10):" is a later addition to the allocate statement. (It is necessary because of polymorphic variables. And its use for specifying the length is a bonus.)

[andrew_4619]

I also think your syntax is invalid.

As a side note I find the "dimension" attribute a bit too verbose and rather unnecessary in the language. In my mind it is a throw back to ancient history. The only benefit I can think of is where you have a long list of variables that all have the same dimensions.

[Johannes_Rieke]

Thanks all,

the dimension attribute seems not to be allowed at all in an allocation statement. It does not work for real kinds, too. I agree, that this seems to be wrong syntax and the compiler correctly gives an error.

The dimension attribute is used widely in text books and I personally like it, because it make the code better readable IMHO. But that's a personal preference...

[Steve_Lionel]

DIMENSION is for declarations - it's fine there, though is generally considered old-fashioned. It's not for ALLOCATE.

[Johannes_Rieke]

Hi Steve,

thanks for clarification. Would you suggest not to use 'DIMENSION' anymore as an attribute or is this just a matter of style?

[Steve_Lionel]

It's just style. My own style is that I may use DIMENSION(:) with POINTER or ALLOCATABLE, but not with fixed dimensions. I'm not consistent about this, though.