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! SYNOPSIS:
!
! # gfortran -o gcd-f gcd.f03
! # ./gcd-f 11 22 33 121
!
program GCD
implicit none
integer, allocatable :: ns(:)
integer :: i, n
character*20 :: tmpstr
n = command_argument_count()
allocate(ns(n)) ! allocate memory for numbers given in command line
do i = 1, n
call get_command_argument(i, tmpstr)
ns(i) = str2int(tmpstr)
end do
print *, gcdn(ns)
deallocate(ns)
! If we declare functions first,
! we have to specify its types within
! the `program' section.
! See http://en.wikibooks.org/wiki/Fortran/Fortran_procedures_and_functions
contains
pure integer function str2int (s)
character*(*), intent(in) :: s
read (s, *) str2int
end function
pure recursive integer function gcd2 (a, b) result(GCD)
integer, intent(in) :: a, b
if (b == 0) then
GCD = a
else
GCD = gcd2(b, mod(a, b))
end if
end function gcd2
pure integer function gcdn(n)
integer, intent(in) :: n(:) ! n is an array
integer :: i
gcdn = n(1)
do i = 2, size(n)
gcdn = gcd2(gcdn, n(i))
end do
end function
end program
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