I would like to create an array with a dimension based on the number of elements meeting a certain condition in another array. This would require that I initialize an array mid-routine, which Fortran won't let me do.
Is there a way around that?
Example routine:
subroutine example(some_array)
real some_array(50) ! passed array of known dimension
element_count = 0
do i=1,50
if (some_array.gt.0) then
element_count = element_count+1
endif
enddo
real new_array(element_count) ! new array with length based on conditional statement
endsubroutine example
Thanks!
Your questions isn't about initializing an array, which involves setting its values.
However, there is a way to do what you want. You even have a choice, depending on how general it's to be.
I'm assuming that the element_count means to have a some_array(i) in that loop.
You can make new_array allocatable:
subroutine example(some_array)
real some_array(50)
real, allocatable :: new_array(:)
allocate(new_array(COUNT(some_array.gt.0)))
end subroutine
Or have it as an automatic object:
subroutine example(some_array)
real some_array(50)
real new_array(COUNT(some_array.gt.0))
end subroutine
This latter works only when your condition is "simple". The allocatable case is much more general, such as when you want to use the full loop rather than the count intrinsic.
In both of these cases you meet the requirement of having all the declarations before executable statements.
[As a side-note, under Fortran 2008 the block construct allows automatic objects even after executable statements.]
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