What is the correct way to initialize a parameter array in fortran?

Question

This works just fine:

  program main
    integer,parameter,dimension(3) :: x = [1,2,3]
    print*,x
  end program main

As does this:

  program main
    integer,parameter,dimension(3) :: x = (/1,2,3/)
    print*,x
  end program main

Is there a reason to think that one form should be preferred over the other (e.g. backward compatibility)?

Solution

The square bracket form was added to the language in Fortran 2003. If you are writing to Fortran 90 (as per the tag on the question) then the square bracket form is a syntax error (square brackets are not in the Fortran 90 character set).

Beyond language standard it a question of personal preference and style.

Comments

[mgilson]

Do you know if there was any reason discussed as to why the language needed a second way to declare an array literal?

[IanH]

Not specifically. I suspect there was no pressing need, just a want, given the single character is more readable and their use is somewhat of a convention across languages.

[mgilson]

That's kind of how I feel about it -- They looked at the language and said "Oops, we goofed up on this one the first time around ... Might as well make a second way to do it ...". sigh However, since I'm trying to target f90-f95, I suppose I'll stick with the ugly version. Thanks. +1 and checkmark to you.

[Bálint Aradi]

Probably they wanted to avoid the occurance of too many subsequent parantheses: call somearrayfunc((/ 1, 2, 3 /)) versus call somearrayfunc([ 1, 2, 3]). For me at least, the 2nd form is more readable.

[max]

I believe this has been introduced with Coarrays in mind.