program ordinavett
!
!  legge un file di coppie di numeri e le ordina
!  a x crescente
!  i vettori passano ai sottoprogrammi in forma esplicita
!

integer, parameter :: idim=10
real, dimension(idim) :: x,y
integer :: n,i

call readdati(x,y,n,idim)
call ordina(x,y,n)

do i=1,n
   write(6,'(2f8.2)')x(i),y(i)
enddo

end program ordinavett

subroutine readdati (x,y,n,idim)

integer, intent(OUT) :: n
integer, intent(IN) :: idim
real, dimension(1) :: x,y

integer :: iend

do i=1,idim
   read(5,*,iostat=iend)x(i),y(i)
   if(iend /= 0)exit
enddo
if(iend > 0)then
   write(6,*)'Errore di lettura :',iend
   stop
endif
if (i > idim)then
   write(6,*) 'errore :numero dati >= ',idim
   stop
endif
n=i-1
end subroutine readdati



subroutine ordina (x,y,n)

integer, intent(IN) :: n
real, dimension(1),intent(OUT):: x,y

real::t
integer::i,j
write(6,'(i2,10f5.1)')0,(x(i),i=1,n)

do j = n-1, 1 , -1
   do i=1,j
      if(x(i) > x(i+1)) then
         call scambio(x(i),x(i+1))
         call scambio(y(i),y(i+1))
      endif
   enddo

write(6,'(i2,10f5.1)')j,(x(i),i=1,n)

enddo


end subroutine ordina


subroutine scambio(v1,v2)

implicit none
real :: v1,v2,t

t=v1
v1=v2
v2=t

end subroutine scambio