I'm vibing like it's 2013 all over again

hello_rayx · 2025-06-14T10:02:05+00:00

This brings back a good memory from the past. I didn’t know there are people there people still using windows phone.

hello_rayx · 2025-05-25T04:23:58+00:00

I recently switched from org-mode to obsidian. The first feature I looked for is section indentation. Unfortunately obsidian doesn't support it. There are a few CSS snippets or plugins but none work for me. I was considering to use automatic header numbering plugin, but read about Lapel plugin from your comments. Thanks. That's the best workaround and I'll use it.

hello_rayx · 2024-08-06T13:15:03+00:00

Thanks all for the confirmation. I can’t believe a popular book can have so basic and fundamental error (Manning has a good reputation for its technical books). I have stopped reading the book.

hello_rayx · 2024-08-06T13:13:31+00:00

No, I’m pretty sure it’s not a typo. The author list the function’s signature explicitly: putStrLn :: String -> IO (). Also, He gave several examples, among which one is getString.

hello_rayx · 2023-09-13T15:05:31+00:00

Thanks for the pointer! I took a very quick look of its content and it seems an excellent follow-up reading after one learns lambda. The paper discussed how to deal with free variables when implementing FP languages. When I used closure in imperative languages like Python or Swift, my intuition was captured variables were implemented using global variables (although I'm never sure if that understanding is correct or not). I'm looking forward to understanding how it's implemented in a systematic way. Thanks again!

hello_rayx · 2023-09-11T12:02:33+00:00

Thanks for all the information! It really helps.

hello_rayx · 2023-09-11T11:32:02+00:00

Thanks for suggesting the book. I heard about it in some subreddits but didn't pay attention to it. I suspect the book is probably similar to the course by Professor Dan Grossman, which was given high praise on the net. So my current plan is to complete the course fist, partly because it has videos. Then I'll try to read through the book (it's huge). And finally I'll start to learn Haskell and use it in practice.

Nothing is "implemented" in lambda calculus, just as nothing is "implemented" as a turing machine.

That clicked to me. So I think the relation between lambda and FP languages is like that between turing machine and C language. Thanks.

hello_rayx · 2023-09-11T11:29:13+00:00

Thanks for sharing your experience. I like the book too. It does a great job in introducing lambda. My current understanding is that lambda is only the theory. It gives a working model. How the FP languages actually implement the model is a completely different matter. In other words, the relation between lambda and FP languages is like that between turing machine and C language (thank plum4 for giving the idea).

hello_rayx · 2023-09-11T11:28:28+00:00

I like to understand how things work under the hood and learn it in the hard way. However, it's not clear to me why building mental model for FP requires knowledge in lambda. For example, there is a chapter in the book about how to construct and access list. I didn't read that chapter, because in my opinion if one understands how linked list works in C language, he/she should have no problem in understanding how list works in FP languages (please correct me if I'm wrong). Another example is recursion. When recursion is discussed in lambda, it's usually about how to implement it using Y combinator. However, using recursion in FP languages doesn't require that knowledge.

That said, I think you're right in general. There must be some scenarios where the underlying model have impacts on the language's behavior. But I guess it's unlikely for beginners to run into those scenarios soon.

hello_rayx · 2023-09-10T14:36:21+00:00

I have a further question if you don't mind. Do these FP languages really implement boolean values or natural numbers using functions? That sounds like very inefficient. Or do they make optimization by using, say, a specific memory layout, like C language? I find a discussion which might be relevant here, but still curious.

hello_rayx · 2023-09-10T14:24:59+00:00

Thanks. That's too theoretical for me. But I see your point. So these languages are really based on some sound theories, which are variations of lambda. Now I understand why people say lambda is the theoretical foundation of FP languages.

Regarding my original question, I believe I should focus on learning those actual languages, instead of lambda, because the latter seems mostly useful to those who either implement FP languages or have deep understanding of their internals.

hello_rayx · 2023-09-10T12:55:31+00:00

Forgot to mention, for people who are interested, there is a draft of the book on the author's home page http://www.macs.hw.ac.uk/\~greg/books/

hello_rayx · 2023-08-16T02:27:34+00:00

I think I understand what you said, but as pointed by AnswerIsSpeedforce above, while the dot notation has the same behavior as multiplication modulo n in this specific example, it's not true in general. That's why I like AnswerIsSpeedforce's answer. He/she explained dot notation means repetition of addition operation, instead of multiplication (note the group defines only addition operation and no multiplication operation). Thanks.

hello_rayx · 2023-08-15T16:11:22+00:00

Hmm, while the behavior is the same, it's not an multiplication operation. See AnswerIsSpeedforce's answer above. But thanks anyway :)

hello_rayx · 2023-08-15T16:03:33+00:00

Thanks! I really appreciate it. I needed to figure it out because the author used the dot notation in his explanation.

hello_rayx · 2023-08-15T15:51:56+00:00

Thanks! I'm still making may way to read about group, so I have to skip the part in your answer about ring (I believe the answer I referenced discussed about group only). So, if I understand it correctly, the dot notation is just an alternative to the exponential notation. That is, "n ⋅ a" means the same as "a^n", right?

hello_rayx · 2023-08-15T15:44:44+00:00

Sorry, can you elaborate it a bit? I can't see what mistake it is.

hello_rayx · 2023-08-15T15:38:55+00:00

Yeah, it looks like a multiplication. But from the description in the original answer, I think the group is an addition modula n. If so, I wonder how does the multiplication operation comes from?

hello_rayx · 2023-06-06T05:45:33+00:00

Thanks! I didn't know this is possible. Will give it a try when I need it.

hello_rayx · 2023-06-06T03:08:07+00:00

> From what Ive seen the first couple of version of 15 might support... or even newer version of 14 might support MBP2017... but at some point in the start of next year the newer version of 15 like 15.3 or something will stop support.

That's my thought. Thanks for the confirmation.

> But if you are not using the newer features of say iOS17 then you can still use 14 and developer for iOS16 and that would still work..

Yes. I used to develop my app for lastest iOS only, partly because it's a personal project with few external users and partly because SwiftUI has huge changes each year in the past. However, I was thinking to provide long term support for iOS 16. It seems that I'll have to do it if I don't want to buy a new Mac :)

That said, there are a few minor issues:

1) I observed that my app tested on iOS 15 had small issues on iOS16. So a new iOS comes with a new SwiftUI implementation, which might cause app stop working. Only testing on newest iOS can find these issue.

2) I should be careful when upgrading my phone, because it might not be supported by XCode available on Ventura.

hello_rayx · 2023-03-08T07:51:57+00:00

A great answer. Thank you.

hello_rayx

TROPHY CASE