module globals
	implicit none
    save
    integer, parameter:: dble = kind(1d0)
end module globals

module NormalDeviates

	use globals
	contains

	subroutine gasdev(harvest)
		use globals

		implicit none
		real(dble), intent(out) :: harvest
		real(dble) :: rsq,v1,v2
		real(dble), save :: g
		logical, save :: gaus_stored=.false.
		if (gaus_stored) then
			harvest=g
			gaus_stored=.false.
		else
			do
				call random_number(v1)
				call random_number(v2)
				v1=2.0*v1-1.0
				v2=2.0*v2-1.0
				rsq=v1**2+v2**2
				if (rsq > 0.0 .and. rsq < 1.0) exit
			end do
			rsq=sqrt(-2.0*log(rsq)/rsq)
			harvest=v1*rsq
			g=v2*rsq
			gaus_stored=.true.
		end if
	end subroutine gasdev
    
end module NormalDeviates

program example
	use NormalDeviates
	implicit none
    
    real(dble) x(300)
    integer i
   
    open(12,file = "data_out.txt")
    do i=1,300
      	call gasdev(x(i))
        write(12,*) x(i)
    end do
    close(12)
    
end program example