Håkan Kjellerstrand

[Neng-Fa Zhou]

I am deeply saddened to learn that Håkan Kjellerstrand passed away on February 10. Håkan, a dedicated professional software engineer, played an important role in shaping the Picat language and system from its earliest days. He wrote more than a thousand Picat programs, and contributed countless suggestions and bug reports. He also co-authored several publications on Picat, including the book "Constraint Solving and Planning with Picat". In addition, he generously provided timely and thoughtful responses to questions on the newsgroup. His passing is a tremendous loss to the Picat community, and he will be remembered for his contributions, generosity, and passion.

Best regards,

Neng-Fa

[Sergii Dymchenko]

Very sad news.

-Sergii.

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[Doug Edmunds]

His personal website, hakank.org appears to be down, but the many programs he wrote are still available on github.  https://github.com/hakank/  
https://github.com/hakank/hakank/archive/refs/heads/master.zip
https://github.com/hakank/hakank.git

[C. G.]

I am so sorry to hear this, even delayed. I'm proud we coauthored a paper. I wish I could have known him better, he was really very passionate and very knowledgeable about the whole CP field and about programming languages for CP. I guess many people know him because of his website. I hope his git repo will remain longer active as it seems to mirror well the content of the website. 

best regards,

Cristian

[Claudio Cesar de Sa]

Hi everyone

I had been away from this mailing list since December due to some email configuration issues.
Just last week, I was thinking about writing to Håkan, and today I came across the news of his passing.
I am truly without words.

I did not know Håkan personally, but I had been exchanging messages with him since 2010 and learned a great deal from him.
 He introduced me to the Picat language, and beyond that, we shared many discussions about code and constraint programming models.
He really helped me in many situations.

His loss is immeasurable for the CP community. He was widely known through his extensive repositories across
many programming languages, and his contributions reached far beyond any single community.

Did anyone here know him personally? Does anyone have more details about his passing?
I will also check his Facebook page in case there is any information there.

This is truly a very sad day and a great loss for all of us.

Finally, we are all subject to forces beyond our control.
My thoughts, prayers, and heartfelt condolences go out to Håkan’s family.


Sincerely,

Claudio

[Magnus Bodin ☀]

ti 24.3.2026 klo 2.31 Claudio Cesar de Sa (ccs...@gmail.com) kirjoitti:

Did anyone here know him personally? Does anyone have more details about his passing?
I will also check his Facebook page in case there is any information there.

This is truly a very sad day and a great loss for all of us.

Hi everyone, 

Håkan was a kind mentor in my office around 1997. We loved tea and Perl back then. 

Even if I left that company, we kept meeting around common interests like philosophy, mathematics, computers and magic.

Håkan was struck with cancer some time ago. He was very well treated, and fighted it out. 

I had the opportunity to get Håkan to give a CP-lecture at the Swedish Mensa Annual Gathering in Malmö, which 2023 just happened to take place across the street from where he lived, in Malmö, here in the south of Sweden.

It was very well received.

In late 2025, the cancer came back and gave Håkan a lot of pain. Our last contact was when he celebrated his 69th birthday in january.

I will never forget his kindness and generosity. 

-- magnus