In principal when a module goes out-of-scope, the variables of that module become undefined — unless they are declared with the SAVE attribute, or a SAVE statement is used. “Undefined” means that you are not allowed to rely on the variable having the previous value if you again use the module — it might have … Read more
The easiest way is like this (reverse the order of indexes for row and column if necessary and add declarations for all variables I skipped to keep it short). It first reads the file and determines the number of lines. Then it rewinds the file to start from the beginning and reads the known number … Read more
The number 865398.78 is represented in single precision in your code. Single precision can handle about 7 significant digits, while your number has 8. You can make it double precision by writing x=x+865398.78_8
You are correct that m31tensorprod being an internal function means that you do not have to declare it in the main program. In the jargon: it has an explicit interface. However, that is not the problem with your code. What is going wrong is with the function definition itself. [Admittedly the compiler message isn’t too … Read more
Here is a Stack Overflow question with some code examples showing several ways of using Fortran allocatable arrays: How to get priorly-unkown array as the output of a function in Fortran: declaring, allocating, testing for being already being allocated, using the new move_alloc and allocation on assignment. Not shown there is explicit deallocation, since the … Read more
According to The Fortran 2003 Handbook by Adams, et al., there is one difference between an intent(inout) argument and argument without specified intent. The actual argument (i.e., in the caller) in the intent(inout) case must always be definable. If the intent is not specified, the argument must be definable if execution of the subroutine attempts … Read more
With RESULT(FluxArray), fluxArray is the name of the result variable. As such, your attempt to declare the characteristics in the result clause are mis-placed. Instead, the result variable should be specified within the function body: function Flux(W1,W2) result(fluxArray) double precision, dimension(3), intent(in)::W1, W2 double precision, dimension(3) :: fluxArray ! Note, no intent for result. end … Read more
I used to just do use modulename – then, as my application grew, I found it more and more difficult to find the source to functions (without turning to grep) – some of the other code floating around the office still uses a one-subroutine-per-file, which has its own set of problems, but it makes it … Read more
This is an arithmetic if statement from FORTRAN 77. Adapted from the FORTRAN 77 specification (emphasis mine): The form of an arithmetic IF statement is: IF (e) s1 , s2 , s2 where: e is an integer, real, or double precision expression s1, s2, and s3 are each the statement label of an executable statement … Read more
There’s no problem having a function return an array, as with this question and answer: the main issue is that you need the function to be in a module (or contained within the program) so that there’s an automatic explicit interface: (Edit to add: or explicitly defining the interface as with Alexander Vogt’s answer) module … Read more