Re: learning functions

[Jerry DeLisle <jvdelisle at verizon dot net>]

RadSurfer wrote:
> Error messages I get are found below.
> I need to learn how to do Functions (and Subroutines) in Fortran.
> I am compiling this as .f95
>
> I do not understand why I am getting so many errors,
> nothing I do seems to reduce them; only increase them! 
You really need to get a good book or google for some on line tutorials.

I took the liberty to clean up your code, by example it will show you some 
things.  Its not useful yet, but there are no compile errors at the moment.

Jerry
! sat 01 sep 2007 09:11:37 pm edt 
! convert to/from gregorian/julian dates
! jgreg.f95

program jgreg
  implicit none

  real(8) jd, m, d, y
  integer n,c
  character arg*80,astr*45,buffer*256

  n = iargc()

  if (n == 1) then
    call getarg(1, arg);
    read(arg,*) jd  ! get cmdline value (real8)
    ! write(*,*) 'fraction ',fraction(jd);
    ! jdtomdy(m,d,y)
  else
    if (n == 3) then
      call getarg(1, arg);
      read(arg,*) m  ! get cmdline value (real8)
      call getarg(2, arg);
      read(arg,*) d  ! get cmdline value (real8)
      call getarg(3, arg);
      read(arg,*) y  ! get cmdline value (real8)
      ! jd = mdytojd(m,d,y)
    else
      write(*,*) 'error: improper number of aruments!'
    end if
  end if

contains

function fix(x)
  real(8)               :: fix
  real(8), intent(in)   :: x

  if (x .lt. 0.0_8) then
    fix = ceiling(x)
  else
    fix = floor(x)
  end if
end function fix

function jdtomdy(jd,m,d,y)
  real(8)                :: jdtomdy 
  real(8), intent(in)    :: jd    
  real(8), intent(in out):: m,d,y 
  
  ! no code yet
  jdtomdy = 0.0_8
end function jdtomdy

function mdytojd(m,d,y,jd)
  real(8) :: mdytojd 
  real(8) :: m,d,y  
  real(8) :: jd 

  if (m<3.0) then 
    y=y-1; m=m+12.0;
  end if 

  jd = fix(y/100.0_8)

  jd = ( 2.0 - jd + fix(jd/4.0))  + fix(365.25*y)  &
        + fix(30.6001*(m+1.0)) + d + 1720994.5

  mdytojd = jd
end function mdytojd

end program jgreg