Henry Simpson
hsimpson88 at hotmail.com
Thu Sep 11 10:55:51 CDT 2003
The manner in which a form or report open event cancel parameter appears to operate is as a boolean. Passing in a zero permits the object to open and a non zero numeric cancels the opening. Microsoft declares this parameter as an Integer likely because the boolean datatype was added to the VBA language after the Cancel parameter was first created and was left in place for backward compatibility. In fact the compatiblity goes back to the 16 bit versions of Access so we continue to see this kind of anomaly. Why something as fundamental to the OS as mouse location parameters, where events fire many times per second, are still singles (and integer for the button parameters) is less defensible if longs are measurably more effiicient than other datatypes. I did a little test with the cancel parameter in a form. I dimensioned a long variable and set it to zero and set the cancel paramter to the long and the form opened witout error. When I set the variable to 64,000 the open event cancelled and when I tried 200,000, an out of range error was raised rather than a data type error. This suggests to me that there was an attempt to coerce a datatype conversion on the Long variable to match the integer type of the cancel parameter before passing to the procedure. If you are using a long variable to a procedure expecting an integer, then the probable sequence of events is: Parameter type demotion Pass to procedure Conversion to Long by OS for CPU manipulation whereas if you begin with an integer type rather than a boolean or a long, you skip the first type conversion and perhaps the procedure runs a few picoseconds faster. While this is hardly proof of the issue it renders your assertion that longs are always faster suspect. I made a post earlier this week that I generally use longs given a choice because they are inherently faster in a 32 bit environment and that is the basis of my 'preference' but I also believe it is better to play safe and match the datatypes of a procedure defined by Microsoft developers. Better and perhaps also faster. Hen >From: Drew Wutka <DWUTKA at marlow.com> >Reply-To: Access Developers discussion and problem >solving<accessd at databaseadvisors.com> >To: "'accessd at databaseadvisors.com '" <accessd at databaseadvisors.com> >Subject: RE: [AccessD] ReadDirectoryChangesW, not returning anything to t >he buffer. >Date: Wed, 10 Sep 2003 23:18:46 -0500 > >It shouldn't even be a preference. Longs are faster in a 32 bit system, so >unless it's absolutely necessary to use an Integer (API Calls), there is >really no reason to use an Integer. > >Drew > >-----Original Message----- >From: Henry Simpson >To: accessd at databaseadvisors.com >Sent: 9/10/03 11:09 PM >Subject: RE: [AccessD] ReadDirectoryChangesW, not returning anything to t >he >buffer. > >Odd. Although I have a preference for longs myself, it turns out that a > >number of standard Access functions use other numeric types so there is >little need to look for old API calls to run into these. For example, >the >mouse cooridinate parameters in a mouse move, down or up event are >singles >even though the values are always 'whole' numbers while the button and >shift >parameters are integer types. The standard cancel parameter for open >events >is also typed as an integer and you had better dimension a compatible >numeric type if you are passing a value to one of these standard >procedures >as a variable, though the mouse parameters are technically return or >read >only values 'returned' by a sub procedure. My rule is to use a >compatible >type and if a long will work, that's the ticket. > >Hen > > > > >From: Drew Wutka <DWUTKA at marlow.com> > >Reply-To: Access Developers discussion and problem > >solving<accessd at databaseadvisors.com> > >To: "'Access Developers discussion and problem solving'" > ><accessd at databaseadvisors.com> > >Subject: RE: [AccessD] ReadDirectoryChangesW, not returning anything >to t > >he buffer. > >Date: Wed, 10 Sep 2003 18:05:01 -0500 > > > >LOL. Very funny. > > > >I do use int for all integers, because I always dimension as Long, >unless I > >absolutely require an integer (which is only for API calls) > > > >Drew > >_________________________________________________________________ >The new MSN 8: smart spam protection and 2 months FREE* >http://join.msn.com/?page=features/junkmail > >_______________________________________________ >AccessD mailing list >AccessD at databaseadvisors.com >http://databaseadvisors.com/mailman/listinfo/accessd >Website: http://www.databaseadvisors.com >_______________________________________________ >AccessD mailing list >AccessD at databaseadvisors.com >http://databaseadvisors.com/mailman/listinfo/accessd >Website: http://www.databaseadvisors.com _________________________________________________________________ Help STOP SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail