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A tail calling interpreter for Python (already landed in CPython)

(blog.reverberate.org)
122 points phsilva | 6 comments | 17 Feb 25 07:12 UTC | HN request time: 0.02s | source | bottom
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thunkingdeep ◴[20 Feb 25 03:19 UTC] No.43110710[source]▶
This does NOT mean Python will get Tail Call Optimization, as Guido cannot be shown The Light, and has decided.
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ehsankia ◴[20 Feb 25 03:39 UTC] No.43110832[source]▶
Guido is no longer BDFL though, it's the steering committee that decides.
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riffraff ◴[20 Feb 25 06:15 UTC] No.43111674[source]▶
the steering committee seems way less conservative than Guido, right?

Looking at python from the outside a lot of changes since GvR stepped down seem like stuff he'd not have been fond of.

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pansa2 ◴[20 Feb 25 06:32 UTC] No.43111761[source]▶
Any examples? The biggest change since Guido stepped down has been the addition of pattern matching, which he was strongly in favour of.

Moreover, Guido is in favour of ongoing addition of major new features (like pattern matching), worrying that without them Python would become a “legacy language”:

https://discuss.python.org/t/pep-8012-frequently-asked-quest...

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1. pinoy420 ◴[20 Feb 25 07:17 UTC] No.43111975[source]▶
Pattern matching seems like a cool feature that was added just because it was cool. I think the syntax is really odd too - apparently to “be pythonic”. I really see no use for it other than to “look smart”. The fact that case match (switch case is a much better description) is expanded to practically a huge if else is disturbing. Similarly the walrus operator. Other than an answer to “what is a new feature of python that you like” interview trivia question, really, who has actually used it?
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2. pansa2 ◴[20 Feb 25 08:39 UTC] No.43112467[source]▶
Yeah, it was added to tick the box for people who ask "does Python have pattern matching?"

If you look at the feature in detail, and especially how it clashes with the rest of the language, it's awful. For example:

https://x.com/brandon_rhodes/status/1360226108399099909

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3. kqr ◴[20 Feb 25 11:33 UTC] No.43113510[source]▶
To be fair, "The Substitution Principle" (more commonly known as "equational reasoning" in this context) has never been valid in any languages that aren't... Haskell, and maybe Ada? Any expression that can trigger side effects is an unsafe substitution. (The reason such substitutions are safe in Haskell and Ada is that those languages prevent expressions from triggering side effects in the first place.)
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4. pansa2 ◴[20 Feb 25 12:02 UTC] No.43113692{3}[source]▶
This isn't about general substitutability though, just about naming constants. If you have `case 404:` and you add a named constant `NOT_FOUND = 404`, you can't change the code to `case NOT_FOUND:` because that completely changes its semantics.

Given that one of the fundamental rules of programming is "don't use magic numbers, prefer named constants", that's terrible language design.

5. Qem ◴[20 Feb 25 12:22 UTC] No.43113858[source]▶
> Similarly the walrus operator. Other than an answer to “what is a new feature of python that you like” interview trivia question, really, who has actually used it?

At least in my case I use it all the time, to avoid duplicated operations inside comprehensions.

6. dragonwriter ◴[20 Feb 25 15:33 UTC] No.43115920[source]▶
I don't use pattern matching much, but I use walrus fairly regularly.