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“I'm basically giving myself a permanent vacation from being BDFL”

(mail.python.org)
2024 points randlet | 4 comments | 12 Jul 18 15:22 UTC | HN request time: 0.64s | source
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js2 ◴[12 Jul 18 16:15 UTC] No.17516019[source]▶
Background ("PEP 572 and decision-making in Python"):

https://lwn.net/Articles/757713/

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jcelerier ◴[12 Jul 18 16:26 UTC] No.17516132[source]▶
> The problem with the C-style of assignments is that it leads to this classic error: if(x = 0) {...}

yeah, if you code on 20 years old compilers with no warnings. GCC 4.1 warns about this (with -Wall) and Clang 3.4 warns about this too, without any warning flag.

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1. iainmerrick ◴[12 Jul 18 19:16 UTC] No.17517715[source]▶
What do you do if you really do intend the assignment?

(Assume for the sake of argument it’s some more reasonable example like "if (x = re_match(foo, bar)) {...}")

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2. 613style ◴[12 Jul 18 19:30 UTC] No.17517838[source]▶
You wrap it in parens to avoid the warning: if ((x = 7)) { ... }
3. Tyr42 ◴[12 Jul 18 19:36 UTC] No.17517895[source]▶
You do "if (((x = re_match(foo, bar))) {...}".

At least the systems I've seen need a extra (()) around = to disable the warnings and notify the reader that you're not just comparing for equality.

4. thestoicattack ◴[12 Jul 18 20:17 UTC] No.17518252[source]▶
C++17 has if-statement initializers, so you can do

    if (auto x = re_match(foo, bar); x.has_value()) {
(or x.ok() or whatever the name is of the method that tells you the validity of x)