Hacker News: renhanxue

New comment by renhanxue in "An Introduction to Writing Systems and Unicode"

renhanxue — Wed, 01 Apr 2026 20:30:18 +0000

That's not really accurate. An overwhelming majority of the simplified characters have had their own code points in Unicode ever since 1.0. Some more details here: https://r12a.github.io/scripts/chinese/

New comment by renhanxue in "Ireland shuts last coal plant, becomes 15th coal-free country in Europe (2025)"

renhanxue — Tue, 10 Mar 2026 10:45:11 +0000

I mean, you can call it a "mountain" of greenwashing but to me it looks more like a mole hill. Total Swedish electricity production is typically 160 to 165 TWh per year and total consumption is usually between 135 and 145 TWh.

In 2025, the net export was about 33 TWh. Gross import from Germany, Poland and Lithuania, including transit to other countries, was 1 TWh. So, imported power from countries with coal power plants was less than 1% of total consumption, and the amount of fossil free power exported was more than 30 times greater than the amount of (potentially) fossil power imported. 1-2% fossil energy in the mix is to me not really significant, and especially not considering how much fossil free power is exported.

Sources:

Statistics Sweden table of power import and export: https://www.scb.se/hitta-statistik/statistik-efter-amne/ener...

Basic information about Swedish power generation: https://www.energiforetagen.se/energifakta/elsystemet/produk...

New comment by renhanxue in "Ireland shuts last coal plant, becomes 15th coal-free country in Europe (2025)"

renhanxue — Tue, 10 Mar 2026 10:06:30 +0000

That may be true in many places, but the Swedish forestry industry is very big, and the district heating plants really do burn mostly forestry byproducts. Of all the biofuel used in Sweden (not just for energy generation), 75% comes from forestry products, and the vast majority of it is either unrefined wood products or byproducts from Kraft process paper manufacturing (like tall oil and turpentine etc).

Specifically in district heating, 87% of the forestry-sourced fuel is unrefined wood products. Almost half of it is just bark, branches and treetops. Of all the biomass in an average mature tree logged in Sweden, 43% ends up as pulpwood, 43% as saw timber, 8% gets burned for fuel and the remaining 6% is treetops and branches which also tend to end up burned for fuel.

There is definitely a lot of debate in Sweden about sustainable forestry practices, though. The industry really wants to clearcut everything for convenience, but it's really bad for biodiversity and the general public hates it.

Source: the report Hållbarare biobränsle i fjärrvärmesektorn, Energiforsk 2023; specifically the charts on pages 14 and 15. Link: https://energiforsk.se/media/33316/2023-979-ha-llbarare-biob...

Addendum: I believe there's also been some studies and experiments involving importing olive pits from the Mediterranean olive oil industry for burning in district heating plants, but I don't think it's been done at scale.

New comment by renhanxue in "Ireland shuts last coal plant, becomes 15th coal-free country in Europe (2025)"

renhanxue — Mon, 09 Mar 2026 14:36:05 +0000

For Sweden, the coal plants were exclusively for cogeneration (district heating with electricity as a byproduct) and only used as peaker plants in winter. Some of them still exist but have been converted to burn biofuels instead, mostly woodchips and other byproducts from the forestry industry.

For most practical purposes, Swedish electricity generation has been basically fossile free since the 1980's.

New comment by renhanxue in "Breaking Free"

renhanxue — Fri, 27 Feb 2026 20:19:40 +0000

The Norwegian Consumer Council's entire yearly budget is about 100M NOK, or about $9.5M USD at the current exchange rate. They most assuredly did not spend >$1M USD on a short video clip.

New comment by renhanxue in "The Feynman Lectures on Physics (1961-1964)"

renhanxue — Wed, 11 Feb 2026 21:10:45 +0000

I mean, for the most part the book is an edited transcription of what he said at the lectures (or, in some cases, what a guest lecturer said). But the lectures weren't scripted, and we know this because his lecture notes are preserved[0] and they do not contain anything like he full text of even a single lecture. They're just lecture notes, not a script. And of course, the book also contain a lot of example problems and graphics - those are mostly the work of Bob Leighton, I believe. There's a reason the book has had so many errata corrected over the years: it was never written and edited in the way a book manuscript would've been written and edited.

[0]: https://www.feynmanlectures.caltech.edu/Notes.html

New comment by renhanxue in "The Feynman Lectures on Physics (1961-1964)"

renhanxue — Wed, 11 Feb 2026 08:40:24 +0000

> The speaker says that Feynman didn't write the Feynman lectures. Wrong.

No, she's right, just talking about a different thing.

"The Feynman Lectures on Physics" is a physics textbook. [0] He did prepare his own lecture material, but he did not write the book.

[0]: https://en.wikipedia.org/wiki/The_Feynman_Lectures_on_Physic...

New comment by renhanxue in "The biggest heat pumps"

renhanxue — Wed, 17 Dec 2025 10:09:43 +0000

Most district heating systems in the Nordics are publicly owned, in part or in full. There are also price controls for the privately owned ones.

New comment by renhanxue in "The biggest heat pumps"

renhanxue — Tue, 16 Dec 2025 23:35:16 +0000

Maybe. I guess it's easier to handle in treated form though. At the point where it gets to the facility it's actually not really sewage anymore, it's just clean water, so after passing the heat pumps it's just released into a nearby lake via a small turbine (both the sewage treatment plant and the heating plant ar located above the water level of the lake).

New comment by renhanxue in "The biggest heat pumps"

renhanxue — Tue, 16 Dec 2025 18:51:09 +0000

Sweden's first commercial nuclear plant[0] was built right next to a newly constructed suburb precisely so that it could be used for district heating too. And also for producing small quantities of weapons grade plutonium, for... research purposes. Waste not, want not!

(It didn't last very long and was shut down in the mid 1970's, for somewhat obvious reasons.)

[0]: https://en.wikipedia.org/wiki/%C3%85gesta_Nuclear_Plant

New comment by renhanxue in "The biggest heat pumps"

renhanxue — Tue, 16 Dec 2025 18:38:34 +0000

Looks like the expansion to 300 MW will have Stockholm beat soon if it hasn't already happened! Or is that in a different plant? Wasn't entirely clear to me, but great progress nonetheless!

New comment by renhanxue in "The biggest heat pumps"

renhanxue — Tue, 16 Dec 2025 18:23:16 +0000

Those are some big heatpumps, but in terms of installed capacity at a single location they have yet to beat the Stockholm municipal heating utility's installation at Hammarbyverket, which since its most recent expansion in 2013 has a total of 7 heat pumps capable of extracting up to 225 MW of heat energy from treated sewage. The utility claims it is (still) the world's largest heat pump installation. Notably it actually uses both the hot and the cold side of the heat pumps; the cold side is sent into the district cooling network.

New comment by renhanxue in "The biggest heat pumps"

renhanxue — Tue, 16 Dec 2025 18:15:26 +0000

Heating with gas is absolutely not a thing in Sweden, I don't think even a single percentage point of homes use that. Firewood is way more common (it's relatively commonplace in the countryside still). Gas is used for stoves in some older buildings in a few specific cities but is almost extinct in that application too. Heating with gas hasn't really been a thing historically either - at first it was mostly wood, then coal and wood, and then district heating and fuel oil completely took over from the 1950's. For a while in the 1970's resistive electric heaters were popular because electricity was cheap with the then-new nuclear plants, while the oil crisis made oil expensive. That didn't last very long.

New comment by renhanxue in "The biggest heat pumps"

renhanxue — Tue, 16 Dec 2025 18:08:31 +0000

A lot of the Nordic heat pumps are ground source, that is to say you drill a hole a couple of hundred feet down into the bedrock where it's always a bit above freezing and you circulate your heat exchange fluid down there and back up again. Air-source heat pumps are mostly a thing in the southern parts where the climate is relatively mild.

New comment by renhanxue in "Loose wire leads to blackout, contact with Francis Scott Key bridge"

renhanxue — Wed, 19 Nov 2025 23:16:50 +0000

The fuel pump not automatically restarting on power loss may actually have been an intentional safety feature to prevent scenarios like pumping fuel into a fire in or around the generators. Still part of the Swiss cheese model, of course.

New comment by renhanxue in "FFmpeg to Google: Fund us or stop sending bugs"

renhanxue — Wed, 12 Nov 2025 02:12:18 +0000

All of these reports are effectively autogenerated by Big Sleep from fuzzing.

Again, Google has been doing this sort of thing for over a decade and has found untold thousands of vulnerabilities like this one. It is not at all clear to me that their doing so has been all that valuable.

New comment by renhanxue in "FFmpeg to Google: Fund us or stop sending bugs"

renhanxue — Wed, 12 Nov 2025 01:38:22 +0000

There are dozens if not hundreds of issues just like this one in ffmpeg, except for codecs that are infinitely more common. Google has been running all sorts of fuzzers against ffmpeg for over a decade at this point and it just never ends. It's a 20 year old C project maintained by poorly funded volunteers that mostly gives every media file ever the be-liberal-in-what-you-accept treatment, because people complain if it doesn't decode some bizarrely non-standard MPEG4 variant recorded with some Chinese plastic toy from 2008. Of course it has all of the out-of-bounds bugs. I poked around on the issue tracker for like 5 minutes and found several "high impact" issues similar to the one in TFA just from the last two or three months, including at least one that hasn't passed the 90 day disclosure window yet.

Nobody who takes security even remotely seriously should decode untrusted media files outside of a sandboxed environment. Modern media formats are in themselves so complex one starts wondering if they're actually Turing complete, and in ffmpeg the attack surface is effectively infinitely large.

The issue is CVE slop because it just doesn't matter if you consider the big picture.

Some example issues to illustrate my point:

https://issuetracker.google.com/issues/436511754 https://issuetracker.google.com/issues/445394503 https://issuetracker.google.com/issues/436510316 https://issuetracker.google.com/issues/433502298

New comment by renhanxue in "Unicode Footguns in Python"

renhanxue — Thu, 06 Nov 2025 00:46:04 +0000

The article has good tips, but Unicode normalization is just the tip of the iceberg. It is almost always impossible to do what your users expect without locale information (different languages and locales sort and compare the same graphemes differently). "What do we mean when we say two strings are equal" can be a surprisingly difficult question to answer. It's practical too, not philosophical.

By the way, try looking up the standardized Unicode casefolding algorithm sometime, it is a thing to behold.

New comment by renhanxue in "Offline card payments should be possible no later than 1 July 2026"

renhanxue — Sat, 04 Oct 2025 12:28:05 +0000

In the EU the authorities have recognized the power of the card networks and introduced price controls on interchange fees in 2015, capping them at 0.2% for debit cards and 0.3% for credit cards.

New comment by renhanxue in "Offline card payments should be possible no later than 1 July 2026"

renhanxue — Sat, 04 Oct 2025 12:17:42 +0000

Generally there are never any transfer fees for private individuals doing domestic transfers. The banks just provide that service for free and eat the cost. Businesses wanting to accept payments via the Swish app usually pay a flat rate of the equivalent of approximately USD $0.15 per transaction (exact terms depends on which bank you use).

It's also worth noting that credit card interchange fees are price controlled in Europe; there's a EU directive that caps the interchange fees at 0.2% for debit cards and 0.3% for credit cards. Because of this, cashback on credit cards is pitiful in the EU; you can get 0.5% cashback but not much more than that.