Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!unmvax!brainerd
From: brainerd@unmvax.unm.edu (Walt Brainerd)
Newsgroups: comp.lang.fortran
Subject: Re: Pointer examples and 8x
Message-ID: <194@unmvax.unm.edu>
Date: 30 Jun 89 23:20:07 GMT
References: <661hallidayd@yvax.byu.edu>
Organization: University of New Mexico at Albuquerque
Lines: 48

In article <661hallidayd@yvax.byu.edu>, hallidayd@yvax.byu.edu writes:
> Chris Torek (chris@mimsy.UUCP), see if the following function is not a
> direct port of your C code (message <18236@mimsy.UUCP>, with corrections
> given in message <18265@mimsy.UUCP>) to Fortran 8x.
> 
>    TYPE (NODE), POINTER FUNCTION  INSERT (HEAD, NEWNODE) ! I believe this to
                ^^^^^^^^^ Can't put this on function line (irregularity?)
>                                                          ! be proper syntax
>                                                          ! for such a FUNCTION
> 
>       TYPE (NODE), POINTER :: HEAD, NEWNODE
>       TYPE (NODE), POINTER :: PTR
>       INTEGER            :: NUMBER = NEWNODE % VALUE   ! I believe the syntax
                   ^^^^^^^
                   , DATA
                   ^^^^^^^ Until recently, it was proposed that
   you could do this with a DATA attribute; now use the old DATA statement.
>                                                          ! allows the initial-
>                                                          ! ization to involve
>                                                          ! the arguments in
>                                                          ! this way.
>                                                          ! (It should.)
> 
>       PTR => HEAD
>       DO, WHILE (ASSOCIATED (PTR % NEXT) .AND. PTR % NEXT % VALUE < NUMBER)
>                                          ! This (and the C code) work
>                                          ! because the .AND. operator
>                                          ! is a "short circuit" form.
                                             ^^^^^^^^^^^^^^^^^^^^^^^^^
>                                          ! (See Ada for a language that
>                                          !  distinguishes between short
>                                          !  circuiting and non-short
>                                          !  circuiting logical operators.)

Nope!  Fortran says things can be evaluated in any order, so this will
not (necessarily) work if PTR % NEXT is not ASSOCIATED.

>          PTR => PTR % NEXT
>       END DO
>       NEWNODE % NEXT => PTR % NEXT
        . . .

This person obviously has gotten the hang of the new pointers.
Glad to see others giving these things a shot to see how they work.

Walt Brainerd  Unicomp, Inc.  brainerd@unmvax.cs.unm.edu
-- 
Walt Brainerd  Unicomp, Inc.  brainerd@unmvax.cs.unm.edu