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Full Discussion: help with data type sizes
Top Forums Programming help with data type sizes Post 302489706 by fpmurphy on Friday 21st of January 2011 10:48:07 AM
Old 01-21-2011
I am going to close this thread. It is veering off-topic.

However I would like to point out that C and C++ have a special type defined for pointer arithmetic, namely ptrdiff_t, which is a typedef of a platform-specific signed integral type.

You can use a variable of type ptrdiff_t to store the result of subtracting or adding pointers as shown in the following simple example:
Code:
#include <stdlib.h>
int main()
{
  int buf[10];
  ptrdiff_t diff = (&buf[4]) - buf;                   // diff = 4
  diff = buf -(&buf[6]);                              // diff =  -6
}

What are the advantages of ptrdiff_t? Self-documenting and portability - the underlying type may vary across programming models but porting requires no source code changes.
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TM::ObjectAble(3pm)					User Contributed Perl Documentation				       TM::ObjectAble(3pm)

NAME
TM::Synchronizable - Topic Maps, trait for storing objects into backends SYNOPSIS
my $tm = .... # get a topic map from somewhere use Class::Trait; Class::Trait->apply ($tm, "TM::ObjectAble"); my %store; # find yourself a proper store, can be anything HASHish # append it to the list of stores, or .... push @{ $tm->storages }, \%store; # prepend it to the list of stores unshift @{ $tm->storages }, \%store; # store it (the proper storage will take it) $tm->objectify ('tm:some-topic', "whatever object or data"); # get it back my @objects = $tm->object ('tm:some-topic', 'tm:some-topic2'); # get rid of it $tm->deobjectify ('tm:some-topic'); DESCRIPTION
This trait implements functionality to store arbitrary data on a per-topic basis. Conceptually, the storage can be thought as one large hash, as keys being use the internal topic identifiers, as values the object data. But to allow different topics to store their object data in different places, this interface works with a list of such hashes. Each hash (native or tied to some implementation) in the list is visited (starting from the start of the list) and can take over the storage. Whether this is based on the topic id, on some other topic information, or on the MIME type of the data (if it has one), is up to the implementation to decide. INTERFACE
Methods storages $listref = $tm->storages This method returns an array reference. You can "unshift" or "push" your storage implementation onto this list. Example: my %store1; push @{ $tm->storages }, \%store1 objectify $tm->objectify ($tid => $some_data, ...); This method stores actually the data. It takes a hash, with the topic id as keys and according values and tries to find for each of the pairs an appropriate storage. If none can be found, it will raise an exception. NOTE: Yes, this is a stupid name. deobjectify $tm->deobjectify ($tid, ...) This method removes any data stored for the provided topic(s). If no data can be found in the appropriate storage, an exception will be raised. object @objects = $tm->object ($tid, ...) This method returns any data stored for the provided objects. If no data can be found for a particular topic, then "undef" will be returned. SEE ALSO
TM AUTHOR INFORMATION
Copyright 20(10), Robert Barta <drrho@cpan.org>, All rights reserved. This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. http://www.perl.com/perl/misc/Artistic.html perl v5.10.1 2010-10-27 TM::ObjectAble(3pm)
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