I've recently learnt about interface blocks when adding a function to my Fortran program. Everything works nice and neatly, but now I want to add a second function into the interface block.
Here is my interface block:
interface
function correctNeighLabel (A,i,j,k)
integer :: correctNeighLabel
integer, intent(in) :: i,j,k
integer,dimension(:,:,:),intent(inout) :: A
end function
function correctNeighArray (B,d,e,f)
character :: correctNeighArray
integer, intent(in) :: d,e,f
character, dimension(:,:,:),intent(inout) :: B
end function
end interface
It appears to me that this may not be the best option.
I've looked into subroutines, but I'm not very confident that it's the right solution. What I'm doing is relatively simple, and I need to pass arguments to the subroutine, but all the subroutines I've seen are a) complicated (i.e. too complicated for a function), and b) don't take arguments. They behave as though they manipulate variables without them being passed to them.
I've not really looked into modules properly, but from what I've seen it's not the right thing to use.
Which should I use when, and how do I go about it best?
Modules are always the right thing to use ;-)
If you have a very simple F90 program you can include functions and subroutines in the 'contains' block:
program simple
implicit none
integer :: x, y
x = ...
y = myfunc(x)
contains
function myfunc(x) result(y)
implicit none
integer, intent(in) :: x
integer :: y
...
end function myfunc
end program
Then the interface of the functions/subroutines will be known in the program and don't need to be defined in an interface block.
For more complex programs you should keep all functions/subroutines in modules and load them when required. So you don't need to define interfaces, either:
module mymod
implicit none
private
public :: myfunc
contains
function myfunc(x) result(y)
implicit none
integer, intent(in) :: x
integer :: y
...
end function myfunc
end module mymod
program advanced
use mymod, only: myfunc
implicit none
integer :: x, y
x = ...
y = myfunc(x)
end program advanced
The module and the program can (actually should) be in separate files, but the module has to be compiled before the actual program.