Has the Fortran committee considered allowing declaring variables anywhere instead of only at the beginning of procedures? This restriction makes it hard to write long procedures with many variables. Seems like another historical baggage just like implicit none.

[image] Beliavsky: Modern Fortran has many features not in f77, such as free source form, end do, allocatable arrays, array operations, derived types, modules, argument intent, etc., that many of us value. According to the Zen of Python, explicit is better than implicit. I believe F77 is mor…

[image] certik: it requires to have a long list of local variables at the top Doesn’t this do what you want? Do i=1,N ; Block Integer, Save :: a=0 ! a retains value calculated across i-iterations and across calls to surrounding program unit. a = some expression + a End B…

[image] fortran4r: I believe F77 is more explicit than modern Fortran. For instance, fixed source form is more explicit than free source form, and you get finer control of which column to write your codes with fixed source form. Similarly, the go to statement is more explicit than exit and cycle…

[image] themos: Doesn’t this do what you want? Do i=1,N ; Block Integer, Save :: a=0 ! a retains value calculated across i-iterations and across calls to surrounding program unit. a = some expression + a End Block; End Do Yes it does. It’s just unfortunate to have to wri…

Another limitation of block for this use case is that if you want to declare a variable near where it’s first used, and you also want to use it further down in the program unit, the block construct may become large. And if you do this for multiple variables that are introduced in several places in t…

[image] milancurcic: I wonder if it’d be possible to create a “Zen of Fortran” that most Fortran programmers would mostly agree on? I don’t think it’s possible, but let’s try: Zen of Fortran

I see: “block myblock” should be “end block myblock”. But j is not an implicit variable - “integer :: j”. I tried a complete version (which had a judiciously placed implict none statement) with gfortran and got the message about j not having a type that I expected. What am I missing? Here is the …

As I understand the block construct, the point is that variables declared within it are only available there; the block is their scope. So you would have to move the end block myblock line below the last use of j. This can get confusing in larger cases, as stated by @milancurcic above .

I’d say this is an argument against long program units in the first place :slight_smile: What I find annoying in Java, C++ or C# code where variables are declared seemingly haphazardly, is that you have to scan the code to find out where these declarations occur. It may be a matter of getting used …

Well, that ought to teach me to always check my code fragments :slight_smile: , especially when demonstrating diagnostic capabilities.

Declare variables anywhere

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certik October 28, 2021, 4:25pm 23

I don’t think it’s possible, but let’s try: Zen of Fortran

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Declare variables anywhere

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