Видео

@@lane1313 I've been learning OCaml in the past few days and been thinking of memory allocation in C. So one thing that strikes me as a beginner is this requesting of memory and then freeing it manually. So let's say I want to do a computation and I request a certain amount of memory. How do I know if that is exactly the right amount of memory I need? And why would I request a certain number that I'm not actually sure about it? It's like, what if I have thousands of such memory allocation requests? What happens when they pile up and maybe I forget to free them? But then it comes to me, why would I do all this manually? It seems like a well-defined programming task to find new ways how to allocate memory. It's like more in a fragmented way, as much as I need, I request, and such. But yeah, I guess I would need to see how garbage collectors are implemented to really know what I'm talking about.

@@domagojding You ask such good questions! "How do I know if that is exactly the right amount of memory I need?" Well, what you'd do is come up with a formula for allocating as much memory as you need. Like, say if I wanted to allocate N amount of integer space. I'd take the amount of items I'd need and multiply it by the size of the type. So I'd do something like `(int *)malloc(N * sizeof(int))` Also, to check that the memory is correctly allocated, you can simply check if the pointer is a null pointer, which is what malloc and calloc return if the memory allocation fails. "And why would I request a certain number that I'm not actually sure about it?" Because this gives you the ability to work on changing values. Data can be inconsistent and volatile, and it's important to allow your memory values to change, like with user input. The user may not always enter something like "test" or "input example". It's fluid and changing, and allowing your program to allow for such changes gives the user more freedom to interact with the program. "What happens when they pile up and maybe I forget to free them?" Well, you'll encounter an issue known as a "memory leak" which is when memory is constantly consumed without being freed. As you've said, there is "garbage collection", which some languages like D implement, which free and manage memory for you. There are arguments as to the benefits and cons of both automatic and manual memory management. Garbage collection gives you the relief of not having to worry about remembering to free your allocations. Whereas manual memory management gives you the freedom to control memory and use it how you see fit. Both ideologies have pros and cons.

@@lane1313 Thank you. I'm kind of still trying to wrap my head around this way of saying the return type, because coming from Haskell, a function is an expression of sort that is reduced to a simpler one or a value, so it's kind of, for now, weird to say what is the return type, but it seems to be that the reduction itself has some kind of a return type, and because the reduction is stateful, so changing something, the return type can be something else, right? So I'm trying to understand the implications of this return expression in C.

@@domagojding So return statements simply mean in layman's terms "Stop what you're doing, and send this back to where it was expected." In functions, return statements state that the function is finished being executed and that either a value, object, or address (if you're returning a pointer of something stored in the heap/dynamic memory region) is to be given back. Same with loops. You can add a return statement in a for or while loop to signify that the loop is to halt and a value is to be stored in whatever scope that it's in. Does that make sense?

@lane1313 You know, the interesting thing is that it does make sense in the sense that the words make sense to me, but I still am having, you know, much difficulty in unwrapping or what would be the best word to, you know, understand this, this, do I call it mental model of evaluation? Because I'm kind of, I'm kind of giving a lot of statements to everyone else, like being a big boss, and from functional programming, which is kind of more, well, maybe that's not fair to say now, but it's, it's like the level of communication is, it's a bit different in the sense that I, I have many functions that do one thing, and if I want to change the output of a function, I transform it or I, well, I transform it in the sense that there is another function that, that externally looks like changing state, but the state is not changed. So it's, I think it's very hard for me now to explain what I mean in a few words, but maybe the, the number of words for now shows, shows still the difficulty in the way I try to understand this imperative model of computation.

@@domagojding I think you should give yourself some credit. You're obviously coming from a different world of programming, and in a sense, throwing yourself into the deep end making a programming language (even if it's just following a guide) in C, which is a whole different programming paradigm. So you should show yourself some grace and continue enjoying the journey of learning C and making this wonderful project. Functions can in fact, do multiple things, however, they can only return one thing at a time when you specify a return type (such as int, float, etc). A return statement can involve an expression (such as for example 5 + a). When the OS reaches the return statement in the stack frame (the stack frame if you're unaware, is the place in memory where the function is being kept. You might learn about function pointers later) it executes the code contained within it one line at a time. If the function has a return type, it'll be expecting a return statement before exiting the scope, which is what the compiler checks for. Once it reaches that return statement, it copies the value that's being returned into memory, and moves it back into the scope where the function was called and if it's being called in an expression like an assignment, it'll be placed where the callee' expects it. This is why you can call different function from within functions and assign values to variables from within functions. Let me know if that doesn't make sense or if I should reword something.

@lane1313 Hello, thank you for the comments. When you say if it makes sense or not, I think it does make sense, but more like I still don't understand, I still don't have the motions, so to say, of how the imperative model works. And I guess I go from word to word, and even if I kind of understand what it does, after I read the whole thing, for example, what you wrote, I'm not sure what I read. And then I go back and I read it, so I guess it just needs more practice, and doing the same thing. So I'll see how it goes. I tried to reflect on what you said in the video, in my newest video, the stream, Build Your Own Lisp, the third part. And yeah, but I'll reread your comment more, and I will let you know how it makes sense, or if rewording something helps. So again, thanks for the comment.

@@hrqmonteiro iosevka

Hi. Yeah Im on Rust book now and will start rustlings too.

@@boxerfencer Yeah, but I was advised to learn, to learn more Rust before I attempt to do something like that, and just today I saw that Tim Clicks in his book, Rust in Action, is also covering some of these things, some of the low-level programming, and also I was looking into FPGAs, and something like connected with Haskell, since basically that's my only background. But so far it seems like I'm going along the Rust book, yeah.

@domagojding that's awesome! Are you planning to do a general purpose OS? Minix re-sparked interest in microkernels, but I feared with Tannenbaum's retirement microkernel interest stalled. With Redox and others such as yourself, not to mention Google's Fuschia , maybe we'll eventually get a microkernel OS for popular use, sooner than later.

@@boxerfencer Hi. Well, I'm nowhere near capable of doing something like that for now, but it's an interesting project of sorts. I found out that I should probably do the MIT operating systems course that, as a teaching device, tries to study and extend the XV6 operating system. So I'm probably going to be doing that. Plus, I'm also rethinking, should I learn some C, because there is so much content about this written in C, and do that along with Rust. But, yeah, it's a fun ride.

Interesting, I commented on this a bit in the next stream, Im curious about the type system, how low can you go with it. Or like with lifetimes which you as a C programmer hold in your head so to say or declare them in rust? Also isnt rust able to go all the way down just like C. Eventually you do assmbley? Also very curious about lisp machines that ran lisp on metal.

Or even.... let f = {a, b, c ? " "}: a + c + b; in f { a = "hello"; b = "world"; c=" --random.spacer-- "; }

aw dandelion haha yeah I see, oh nice hello fleur!

Hey thanks. I think I will be making recap videos of what I have learned since this module system deep dive for example is going to take hours already.

@@domagojding Ah okay. I will wait then until you post a new playlist

garbage

I get that xD I'll try not to too much. Thanks!

Will do. Thanks! Hey I just saw numtide just released github.com/numtide/nix-vm-test

@@domagojding Thanks. Well I just wanted to set up a VM in case I ever felt the need for enhanced security, browsing or whatever. I set up Vagrant and also Qemu.But I doubt it I will use either. Distrobox (&BoxBuddy) meets a present need (a Debian package not in Nixpkgs).

Oooh I will have to check in couple days, Im on a trip. I kinda change fonts sometimes. I use nerd fonts, hm this could be caskydia not sure

oh right! I will keep a note of this. Thank you! Yeah, after I do all these nix dev tutorials I will redo them again but like deep dives so I'll be sure to mention this

Yeah, and payoff is great too. I like how all is so interconnected, programmable interface for your system, so once you start even with home manager, you kinda wish you can go deeper. I think it's a great way to really start interacting with the system, like let's say NixOS modules which are super nice deep thing on it's own, then types of derivations and nix store.. oh it's like a very fertile ground for many ideas. In the end it's all nix expressions all the way you go so anything you learn it's not like wasted, but it expands from anything you know.