recursively take in input file for operation - fortran

Question

I have several input data files with the name angleFile1.dat, angleFile2.dat, angleFile3.dat and so on. (I have more than 100 files)
Each file contain 45000 data of angles. I want to group these angles to get a distribution within 0 to 360 degrees.
I have written a Fortran code to do the job for one file at a time.
This code will read in the input file "angleFile1.dat" and write the distribution (in bins) in the "angleOut.dat" file.
program binangle
implicit none
integer :: i, j, k
integer,parameter :: arr=45000
real,dimension(1:arr) :: aangle
integer,dimension(0:360) :: binaangle
do i = 0,360
binaangle(i) = 0.0
end do
!OPEN OUTPUT FILE
open(unit=49,status="unknown",file="angleOut.dat")
!OPEN INPUT FILE
open(unit=50,status="unknown",file="angleFile1.dat")
read(50,'(F8.3)') (aangle(i), i = 1,arr)
! DO THE BINNING
do j = 1, arr
binaangle(int(aangle(j))) = binaangle(int(aangle(j))) + 1
end do
! WRITE INTO OUTPUT FILE
do k = 0,360
write(49,*) k, " ", binaangle(k)
end do
How to make this code to recursively take in the input files (angleFile1.dat, angleFile2.dat, angleFile3.dat and say until angleFile100.dat) and write the distribution in the same output file?
Help is much appreciated.

Answer 1

Well, one way would be to split the reading into a separate subroutine. Something like (untested):
program binangle
implicit none
integer :: i, k
integer,parameter :: nfiles = 100 ! Use get_command_argument to read the
! value at runtime rather than hardcoded,
! left as an exercise to the reader
integer,dimension(361) :: binaangle
binaangle = 0 ! Use array op rather than manual loop
do i = 1, nfiles
call add_angles_to_bins(binaangle, i)
end do
!OPEN OUTPUT FILE
open(unit=49,status="replace",file="angleOut.dat")
! WRITE INTO OUTPUT FILE
do k = 1, ubound(binaangle, 1)
write(49,*) k - 1, " ", binaangle(k)
end do
contains
subroutine add_angles_to_bins(bins, fnum)
integer, intent(inout) :: bins(:)
integer, intent(in) :: fnum
character(len=200) :: fname
integer, parameter :: arr = 45000
real :: aangle(arr)
write(fname, '(A,I0,A)') 'angleFile', fnum, '.dat'
!OPEN INPUT FILE
open(unit=50,status="old",file=fname)
read(50,'(F8.3)') aangle
close(50)
! DO THE BINNING
do j = 1, arr
binaangle(int(aangle(j)) + 1) = binaangle(int(aangle(j)) + 1) + 1
end do
end program binangle
(One might add that the above suggested solution does not use recursion.)