Archive for the ‘Delphi’ Category
Posted by jpluimers on 2009/05/06
Two days ago, [Wayback] Michael Justin (who just released version 1.7 of the [Wayback] Habari Active MQ Client components) posted a blog entry about a strange circumstance [Wayback] when 1.99 would not compare equally to 1.99.
He tracked it down to the [Wayback] 8087 (more formally: Intel [Wayback] FPU) Control Word being hosed on his system.
I could not reproduce his particular case, but since I have seen similar issues in the past, I wrote the DUnit test case below which shows you what can happen by manually setting the 8087 Control Word.
The difference between the 8087 Control Word values $1372 (default) and $1272 (failure) is the internal mantissa precision (see the [Wayback] “Art of Assembly Language” and the [Wayback] Intel FPU Control Word documentation on this).
Edit: Found a [Wayback] much more complete description of the bits in the FPU Control word.
It changes from 64 bits to 53 bits, which is enough to make 1.99 not equal to 1.99.
I have seen behaviour like this in the past with some networking stacks in the Turbo Pascal 7 era, with some C++ DLL’s in the Delphi 1-3 era, and some printer drivers in the Delphi 5-7 era.
Let me know in the comments (or using the contact form) where you have bumped into this.
The code below makes use of the Jcl8087 unit which is part of the JCL ([Wayback] JEDI Code Library) at [Wayback] SourceForge.
Add the unit to any DUnit test project you created and observe the results.
Read the rest of this entry »
Posted in 8087, Algorithms, Delphi, Development, Floating point handling, Software Development | 8 Comments »
Posted by jpluimers on 2009/05/06
On 20090504, Atozed announced Crosstalk: a technology that allows native Delphi code to consume .NET assemblies in a really intuitive and transparent way.
The announcement contains a FAQ.
It is a promising technology, not only because it is dead easy to use, but also because it is backed by Atozed: a team of people that have made complex technology like Web Apps easy to use by creating IntraWeb.
Expect demos soon (maybe even at Delphi Live!).
Here is a short example:
Read the rest of this entry »
Posted in .NET, Delphi, Development, Software Development | 3 Comments »
Posted by jpluimers on 2009/04/28
I like enums. Maybe because of my Turbo Pascal and Delphi background. They are descriptive. Makes code easier to read.
public enum TrafficLightColors
{
Red,
Yellow,
Green
}
But using them in C# foreach loops is a bit of a pain, not so much in the loop itself, but more in getting the list of values to loop over.
Read the rest of this entry »
Posted in .NET, C# 2.0, Delphi, Development, Software Development | Leave a Comment »
Posted by jpluimers on 2009/04/27
I just tried to elaborate on an answer to a question from Michael Justin on stackoverflow.
(yes, that’s the author of some message broker clients like the Habari ActiveMQ client that allows Delphi applications to talk to the Apache ActiveMQ message queueing broker).
His question is on virtual constructors and class reference: How can I detect if a Delphi class has a virtual constructor?
The combination of class references and virtual constructors is one of the fundaments of how Delphi became Delphi; in simple terms:
- class references allow you to register components on the component palette in Delphi
- virtual constructors allows the designer to construct the instances of those components at design time
That’s why I think it is important to describe the distinction between virtual constructors and regular non-virtual constructors in the answer below (which is a copy of the answer I posted to stackoverflow)
Read the rest of this entry »
Posted in Delphi, Development, Pingback, Software Development, Stackoverflow | Leave a Comment »
Posted by jpluimers on 2009/04/27
Quite a while ago, a co-worker asked how to get tot the Instance variable when using a with statement like this:
function TMyForm.ExecuteForm(FormClass: TFormClass): Integer;
begin
with FormClass.Create(self) do
try
Result := ShowModal;
finally
Free;
end;
end;
So I wrote the blog entry below when I started my blog last week, and set the published date to somewhere early May, a week that will be really busy.
Then I found out about the Stackoverflow question Reference object instance created using “with” in Delphi followed by the answer by user ‘Alexander‘ (a really smart Russian guy).
Enough coincidence to publish the blog article earlier than scheduled :-)
Before I explain why I really hate ‘with’, lets show what my co-worker wanted, and my solution: Read the rest of this entry »
Posted in Delphi, Development, Pingback, Software Development, Stackoverflow | 2 Comments »
Posted by jpluimers on 2009/04/26
On request, I have started to maintain a page about the events I have spoken at or will be speaking at.
The page serves as a central landing spot for people wanting to download materials of past appearances, or wanting to meet me in person on future appearances.
Currently, it contains
I will extend it with more downloads and more events over time (and blog about it when it gets extended).
Drop me a message at the contact form when you need more of the past downloads (I have been speaking at conferencs since 1995, so there is quite a lot of material <g>)
Posted in About, Conferences, Delphi, Development, Event, PowerDay | Leave a Comment »
Posted by jpluimers on 2009/04/26
Oosterkamp training | consultancy (the company that I used to co-own before partnering in better office benelux), together with Barnsten (the CodeGear / Embarcadero representative in the benelux) organized a Delphi 2009 interactive briefing on the evening of April 1st, 2009.
That wasn’t a joke, and we had good attendance with interesting questions.
I did a session on migrating to the most current Delphi version.
Read the rest of this entry »
Posted in Briefing, Delphi, Development, Event, Software Development | 1 Comment »
Posted by jpluimers on 2009/04/24
Somehow I keep forgetting this ‘be aware though’ part below, hence this blog post :-)
When you are developing packages, sometimes you need units that are part of the VCL/RTL source tree.
Normally when compiling such a package, Delphi suggests the depending VCL/RTL package to add to your required package list.
However, that does not always work, especially with design-time packages (those start with ‘dcl’ in stead of ‘vcl’).
The last time I bumped into this was when I developed a package that needed the MessageDigest_5 unit.
Read the rest of this entry »
Posted in Development, Package Development, Software Development | Leave a Comment »
Posted by jpluimers on 2009/04/22
A long time ago, the for ... in statement was added to the structured statements part of the Delphi language. It is a really powerful statement, that allows for code like this:
var
Line: string;
begin
for Line in MyMemo.Lines do
// some business logic
end;
in stead of using the traditional for statement which needs an extra LineIndex variable and an assignment statement:
var
LineIndex: Integer;
Line: string;
begin
for LineIndex := 0 to MyMemo.Lines.Count do
begin
Line := MyMemo.Lines[LineIndex];
// some business logic
end;
end;
So, “for … in” is a cool feature, but now I wanted to do the same for a TPageControl:
Read the rest of this entry »
Posted in Delphi, Development, Software Development | 1 Comment »
Posted by jpluimers on 2009/04/21
I’ll be speaking during DelphiLive ’09 that is held from May 13-16 in San Jose (CA, USA, not any of the other San Jose cities).
This is going to be a top event with really knowledgeable Delphi speakers from all over the world.
Besides the 2 sessions that I’m doing, I’ll be hanging around as are the other speakers.
So feel free to approach us, and learn from the things we learned. Or teach us something new: all of us are eager to learn as well as teach!
The downloads are now available.
Posted in Conferences, Database Development, Delphi, Development, Event, InterBase, Software Development | Tagged: Conferences, Delphi, Travel | Leave a Comment »
The Wiert Corner - irregular stream of stuff 