International Pascal Congress in Salamanca

Dear fellow readers, I'd like to invite you to International Pascal Congress which will happen from 3rd to 7th July this year in beautiful Salamanca, Spain.

(Not sure you want to go to Salamanca? Think again.)

Although the congress has wider target audience than pure Delphi, it is sponsored by Embarcadero and many prominent Delphi speakers will participate. Marco Cantu will be there, as will Daniele Teti and Bruno Fierens. I will also add my contribution.

The program is split between talks (Monday) and many advanced programming courses (Tuesday--Friday) with plenty of time for socializing or for exploring beautiful Spanish country.

Besides the talks and courses and socializing and a dinner, the IPC will also grant a Niklaus Wirth Award for a Most Valuable Contributor to Pascal. They are still accepting nominations.

I hope to see you there as this is a perfect occasion to forget all the Covid craziness and get together again!

"Design Patterns", rescheduled

For the last Delphi meeting in Slovenia this year we have organized a small workshop about Design Patterns. As usual, it is intended for Slovenian programmers and will be given in the Slovenian language.

"Design Patterns" workshop in Ljubljana

For the last Delphi meeting in Slovenia this year we have organized a small workshop about Design Patterns. As usual, it is intended for Slovenian programmers and will be given in the Slovenian language.

We'll meet again (finally)!

After two long-distance years we are finally moving back to normality, starting with a Slovenian RAD Studio meeting next Wednesday in Ljubljana.

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Po dveh letih virtualnih konferenc vas končno spet vabimo na srečanje v živo! Za izgovor za druženje si bomo ogledali novosti v RAD Studiih iz zadnjih dveh let (10.4, 10.4.1, 10.4.2, 11, 11.1), predvsem pa bomo dogodek izkoristili za klepet ob hrani in pijači in ponovno spoznavanje.

Pridružite se nam 25. maja ob 9h! (klikni za več podatkov in prijavo)

Slovenian Delphi 11 Webinar

Just a short notice for Slovenian readers - In case you missed it, next week you'll be able to join a Slovenian webinar about Delphi 11. 

Register here

Readers-writer lock - Part 4: Improving TLightweightMREW

While the TLightweightMREW is quite handy, it is not perfect. There's a weird assymmetry in it. On all operating systems that Delphi can compile for, read locks are reentrant (recursive) while write locks are not. In other words, if a thread already owns a read lock, it can call BeginRead again and it will succeed. Write locks are different. If a thread already owns a write lock and calls BeginWrite again, it will either deadlock (on Windows) or raise an exception (on other supported platforms).

This is, however, relatively simple to fix. I have implemented a simple wrapper for the TLightweightMREW lock in TLightweightMREWEx. This new record uses internal TLightweightMREW to provide locking and adds some simple logic to implement write lock reentrancy. The implementation and accompanying test program rwReentrantWriter can be found at https://github.com/gabr42/examples/tree/master/Reader-writer%20lock.

Readers-writer lock - Part 3: Some numbers

In order to convince you that a readers-writer lock is not a stupid idea, I should finally show some numbers. In this article I'll present a minimalistic (but still real-life) example which allows us to compare different locking solutions.

All code from this article is available in project rwLock at  https://github.com/gabr42/examples/tree/master/Reader-writer%20lock

Readers-writer lock - Part 2: Implementation

In the previous installment I introduced the idea of a readers-writer lock. Today I'll look into readers-writer lock implementations (yes, multiple) that are available in the Delphi run-time library.

Readers-writer lock - Part 1: Why?

One of the pleasant surprises in Delphi 10.4.1 was the addition of a new readers-writer lock implementation TLightweightMREW. While it was probably not noticed by most of the users, I was quite happy to see it implemented. 

So now you are asking yourself - what is this readers-writer lock and why am I so happy to see it in Delphi? Well, I'm glad that you're asking! Let me explain ...

In multithreaded programming (as most of my horror stories start), we frequently run into a problem of resource sharing. Two threads want to modify a shared resource at the same time and that can cause many problems, from information being overwritten to corrupted data and program crashes.

To fix this, we add resource protection. Usually that is just a critical section (typically through a TCriticalSection wrapper), or Delphi's TMonitor. Sometimes, however, protecting resources with a simple critical section causes an unnecessary performance drop, and that's when a readers-writer lock (may) come into play.

OmniThreadLibrary 3.07.8

New OmniThreadLibrary is out! Get it while it’s hot!

Version 3.07.8 is mostly a bugfix release. It fixes few small bugs and enables support for Delphi 10.4.

You can get it now on git, download the ZIP archive, install it with Delphinus or with GetIt (in few days).

For more information, visit OmniThreadLibrary home page or write your question on the forum.

Top three Delphi 10.4 features

Delphi 10.4 has just been released (turn here for a great overview) and has some nice enhancements even for us, die-hard Windows developers. It is too early to give any deep analysis as I have just installed it and did not do any thorough testing, but I can already pick my top three new features. In no particular order, here they are:

Long live Delphi!

Something great has happened on this day, 25 years ago.

It was the sign of Aquarius. People were listening to Creep. And the AppBuilder was released.

You don’t know AppBuilder? Sure you do! It was developed and — thanks to Novell — released under codename Delphi.

Indeed, our beloved Delphi is 25 years old today! A quarter of a century!

Sales! Sales! Sales!

Parallel Programming with OmniThreadLibrary

e-book: 50% off

printed book: 25% off (use coupon BLACKFRIDAY25)

Delphi High Performance

e-book: 72% off

Hands-on Design Patterns with Delphi

e-book: 80% off

ITDevCon X

The ITDevCon X - the tenth edition! - has just ended and boy was it a blast! (As usual, I should say.)

This was my seventh ITDevCon conference and I always like to visit it. This year was no exception.

Thank you Daniele, Valentina, Fabrizio, and all bit Time gals and guys for organizing two days of great fun and great food!

P.S. My slides & code are already available online.

CompareValue for booleans

CompareValue function is incredibly practical when you are writing comparers (functions that determine how some data structure is ordered). System.Math and System.StrUtils define a bunch of functions that can be used to compare integers, doubles, strings … There’s, however, no CompareValue for booleans.

A CompareValue function compares two parameters, traditionally named left and right, and returns 0 if they are the same, –1 if left is smaller and 1 if right is smaller.

If we use the usual ordering of false < true, we can write the missing function as follows:

function CompareValue(left, right: boolean): integer; overload;
begin
  if left < right then
    Result := -1
  else if left > right then
    Result := 1
  else
    Result := 0;
end;

Your task for today – if you choose to accept it – is: Write this function without any if statements.

Visit “What’s new in Rio 10.3.2” in Ljubljana

On September 26^th I’ll talk about RAD Studio Rio in Ljubljana. We’ll discuss 10.3 a bit and 10.3.1/10.3.2 updates in more detail. We’ll also look into the future to see what 10.4 might bring.

This will also be a good opportunity to see my latest book, Design patterns with Delphi, or get your own copy signed.

Participation is free, but you should register here so we can prepare enough food for everyone.

When True is not

Pop quiz! How can the following program …

Writeln(True);
Magic;
Writeln(True);

… output this:?

TRUE
FALSE

Simple!

The case of a missing begin/end

Delphi never stops surprising me …
Did you know that this is a valid syntax?

case a of
  0: Writeln(0);
  else
    Writeln('else');
    Writeln(a);
end;

This code indeed compiles and works exactly as the following fragment.

case a of
  0: Writeln(0);
  else begin
    Writeln('else');
    Writeln(a);
  end;
end;

I personally would never drop begin/end inside a case/else statement, but at least someone must disagree. I found such example in a very (VERY!) old code (it was written for Delphi 2) and I was quite surprised that it compiles at all.

EDIT

Anton Alisov suggested formatting first example as:

case a of
  0: Writeln(0);
else
  Writeln('else');
  Writeln(a);
end;

I guess this makes more sense (but just an itsy bitsy teenie weenie bit more).

Delphi Day 2019 sessions

Slides and code for my Delphi Day 2019 sessions are now online.

Spring4D European Conference 2019 sessions

Slides and code for the Spring4D conference are now published on the conference page.

Slides and code for my two sessions – Design patterns with Spring4D and Interception and dynamic proxy – are also available on my presentations page.