JiscMail Logo
Email discussion lists for the UK Education and Research communities

Help for COMP-FORTRAN-90 Archives


COMP-FORTRAN-90 Archives

COMP-FORTRAN-90 Archives


COMP-FORTRAN-90@JISCMAIL.AC.UK


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

COMP-FORTRAN-90 Home

COMP-FORTRAN-90 Home

COMP-FORTRAN-90  2004

COMP-FORTRAN-90 2004

Options

Subscribe or Unsubscribe

Subscribe or Unsubscribe

Log In

Log In

Get Password

Get Password

Subject:

Re: Symbols

From:

Aleksandar Donev <[log in to unmask]>

Reply-To:

Fortran 90 List <[log in to unmask]>

Date:

Wed, 3 Mar 2004 12:03:12 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (64 lines)

Hello,

The % is there to stay folks. Time cannot be reversed as far as I
know...If someone wants to contribute to Fortran, think about what can
be done to improve the language, not your cosmetic personal preferences.
Van and Lawrie both had good points, but I am not convinced that adding
a second syntax now to correct some of the problematic original
decisions is a good thing due to duplicity...

Alvaro Fernandez wrote:
> It's not insurmountable, but if the code was written e.g. assuming that
> random access to entries was essentially free, such an assumption would have
> to be revisited - and you end up coding differently anyway. So what did the
> accessor gain you, then? Of course, if properly written, you wouldn't be
> hopping around too much anyway... I don't know. It seems that it's not that
> easy to isolate the repercussions of such changes in underlying assumptions.
Well, nothing is easy if you want both abstractions and efficiency.
But there are many cases where indeed you can preserve both speed and
abstraction.

For example, assume that you have a data structure where you have
objects numbered from 1 to N, but you don't really know what N is, i.e.,
N may grow (think of sparse matrix factorization, for example). One
approach will make a big array of these things and use direct indexing
into it. This will be better when you have a good upper bound on N (if N
crosses your bound, reallocate and copy the array). But if you don't
have a good bound on N or want to conserve memory, you can allocate
things in blocks, and change your array component into an
accessor/updater function. This will still be efficient, modulo the
extra procedure call, which can be avoided by inlining, since converting
an index into the memory address is easy: Divide with the block size to
find which block to look in, and then where in the block to look.

There are ways to do something like this in future Fortran without
accessor/updater functions. What needs to be allowed is to use a
pointer-result function reference as if it is a variable:

type :: t
    real :: x
end type

function p(i)
    integer :: i
    type(t), pointer :: p
    ...
end function

p(3)%x=3.0 ! Updater
write(*,*) p(3)%x ! Accessor

The exact same would work if I make p an array:

type(t), dimension(100) :: p
p(3)%x=3.0 ! Updater
write(*,*) p(3)%x ! Accessor

By using type-bound procedures (Fortran 2003 OOP) and this kind of
feature one can almost emulate updater/accessor methods. I can give the
example, but since most readers likely do not know F2003 yet, it is
unlikely to be useful.

Best,
Aleks

Top of Message | Previous Page | Permalink

JiscMail Tools


RSS Feeds and Sharing


Advanced Options


Archives

December 2023
February 2023
November 2022
September 2022
February 2022
January 2022
June 2021
November 2020
September 2020
June 2020
May 2020
April 2020
December 2019
October 2019
September 2019
March 2019
February 2019
January 2019
November 2018
October 2018
September 2018
August 2018
July 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
December 2015
November 2015
October 2015
September 2015
August 2015
June 2015
April 2015
March 2015
January 2015
December 2014
November 2014
October 2014
August 2014
July 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
July 2013
June 2013
May 2013
April 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
August 2010
July 2010
June 2010
March 2010
February 2010
January 2010
December 2009
October 2009
August 2009
July 2009
June 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
January 2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997


JiscMail is a Jisc service.

View our service policies at https://www.jiscmail.ac.uk/policyandsecurity/ and Jisc's privacy policy at https://www.jisc.ac.uk/website/privacy-notice

For help and support help@jisc.ac.uk

Secured by F-Secure Anti-Virus CataList Email List Search Powered by the LISTSERV Email List Manager