/prog/ - Programming

how about

>have an actual goal

>learn what you need in order to achieve that goal

>>3752

I've just started learning Android development.

I'm stating off with the free Udacity course. It's way slower than I'd like as it is designed for complete programming noobs, but it's material seems to be comprehensive, as I've had little problem following along and building the simple apps.

>>3780

yes same here, just starting out but i've made some simple apps.

maybe we should make this an android app coding thread. and we try to make the most interesting apps and share them.

>text editor

>bold

well you're off to a bad start.

In order to do this, you can't have a single text area. when the user clicks bold you need to add a new DOM element with a bold style, and you need to handle mouse-clicks, arrow movement, selections, etc., to make your dense list of DOM elements function like a single area. it's a tremendous amount of work for literally no payoff: your users would be just as happy typing [b]blah[/b]

>>3777

Ahh so what your saying is when a user clicks the bold button, I'll need to replace the text area in the background? That sounds like a lot of extra work but nothing too bad to be honest.

>>2970

Got a laugh out of me

grep

sed

find

awk

make

ed

man

The most important terminal commands are

[code]\n

\r

\e[30m thru \e[37m

\e[40m thru \e[47m

\e[1m

\e[0m

\e[2J

\e[?25h and \e[?25l

\e[n;mH with n and m as coordinates

\e[s and \e[u

\e[n;mr with n and m as the top and bottom row[code]

That last one is pretty killer.

inb4 curses. You may as well use a fucking web browser.

>>3749

if you haven't read donald knuth's set yet you're pretty much fucked at this point tbh. good luck.

alacrity

fuckin shit

You mean a GUI program?

It might be more complex than you think.

The big standard windowing and GUI APIs are Win32 for Windows, Cocoa for Mac OSX, and Xwin for Linux and BSD (though almost nobody uses Xwin raw).

If you want cross-platform, you should look into GTK or Qt, or even wxwidgets.

Using the libraries and APIs is better unless you need the flexibility. Don't call an external program unless you need to. On top of the pain of fork and execing, it's also much more expensive and far less efficient.

Also, curl is just a thin wrapper around libcurl anyway.

It's hard to know what would be the proper way exactly without knowing your exact use case. The best option, though, is to either use libcurl and readdir/readdir_r for those two uses, or luacurl and luafilesystem, depending on which part of your program and how integrated you want that functionality to be.

You usually don't want to fork and exec unless you want to be able to invoke external functionality dynamically, such as having the user specify a command to use (like with a shell, or with any system that needs user plugins that should be language-agnostic, can work with program output, and don't need real IPC).

Don't call an external command unless you really need to and it fits your workflow. Doing an external call to something like curl or find is redundant, pointless, and prone to way more bugs. Not to mention that the overhead of managing the forked process as a child and making sure it exits properly and everything that goes with it is way more work than just using libcurl and readdir properly.

Here's the basic way with a fork:

int pipefd[2];
pipe(pipefd);

pid_t parent = getpid();
pid_t pid = fork();

if (pid == -1)
{
    // Some error forking
    return 1;
} else if (pid > 0)
{
    // I am the parent
    // Close writing end
    close(pipefd[1]);

    ssize_t newstart = 0;
    char buffer[BUFSIZE];

    while (true)
    {
        // Do the BUFSIZE - newstart - 2 for necessary injected characters, if needed
        ssize_t size = read(pipefd[0], buffer + newstart, BUFSIZE - newstart - 2);

        // This is done because the buffer was already offset.  We want size
    

It just occurred to me that you probably meant calling the script in Lua with pcall or something.

You can do that, but still keep in mind it will be far slower and more prone to bugs. You also have issues if you want to be able to get stdout, stderr, and exit status at once.

It is also worth mentioning that POSIX does have a simpler popen interface that wraps forking and execing. I haven't done POSIX C programming in a while.

Either way, native is always faster than forking. You fork and exec if you need the flexibility to decide certain things at runtime.

Now, practically, it will make little difference as long as find is there and the output is reliable. Objectively, forking is a worse option, but you won't notice a difference in runtime or anything unless you are doing some very heavy CPU-bound work.

I'd say to implement both ways and see what works best for you, if time isn't an issue.

>>3741

Yeah, I'm using system(3) and popen(3) from Lua depending on if I need to get the output.

I'm aware that calling the commands without the popen(3) interface from C is way more tedious, but that isn't the case from Lua, where it's two lines at best.

Thanks for providing your insight. You're right, using the libraries is the preferable way. There's just too many incompatibilities with implementations of commands, and sometimes the commands aren't even available and you just find out during runtime.

However, working in an environment I'm writing shell scripts for anyway (those are way more sensitive to the environment than Lua, and I'm using both curl and find in them) and not wanting to redistribute the lua script, I don't think it really matters in terms of being error-prone. In terms of being cpu-intensive… Again, script argument. Those call a command on nearly every operation. I think that's way more cpu-intensive. (and it doesn't really matter either, it's fast enough). So I can just use any method in this case, while still preferably the library method.

I just have to add one thing: It really depends on whatever you're doing if the readability increases or not (at least in lua). Doing "for file in io.popen("find"):lines()" is way less tedious than the example on the luafilesystem page to recursively iterate over a directory. Same thing goes for curl, really.

>>3744

That's a good point. In the end, whatever gets the job done and doesn't break is preferable if you can get it up and running.

The primary argument to library vs forking for me is flexibility. If you need to do something to files while iterating over them (such as taking a stat of each, or checking extended filesystem attributes), you can more easily do it with the library system.

If you're willing to handle the small performance hit of forking (and to be honest the performance impact of both filesystem access and network transmission are far higher) and you are sure the command syntaxes can be consistent, it's just up to personal preference.

>>3589

>fucking hate falsiness

>null should be falsy

I hate gets() and scanf(). In CURRENT_YEAR, these libc functions should do nothing but cause a compile-time error, telling you to use shit that isn't fundamentally insecure (in the case of gets) or fundamentally incapable of interacting reasonably with a user (in the case of scanf). Read in lines at a time, into buffers that can contain those lines, and use sscanf() on read lines if you really want that shit.

I hate how every 'modern' 'advanced' 'high-level' programming language is stuck in the 90s. The Linux kernel continues to advance. It has all kinds of cool system calls. You can do shit like swap the names of two files without a race condition. But fuck it, Windows doesn't have that, and it wasn't portable among unices back in 1995.

oops that second one wasn't a future.

Replacement hate: laziness.

It is the solution for literally nothing, but it introduces all kinds of problems of its own.

>>3722

Null being falsy is unambiguous in almost every case.

>waah waah languages arent 100% theoretically correct

Fucking pretentious losers in this thread, what have you accomplished besides bitching?

https://en.wikipedia.org/wiki/Parkinson%27s_law_of_triviality

Go and write something more complex than "hello world" to have some weight behind your words before you act like a software god. Your code probably runs like shit, and that's not because gets() and scanf() suck, >>3722

>>3728

I'm a professional programmer who has to use dozens of languages through work; you get a long list of things to hate when you have to use tons of different languages in codebases written by other people.

Why are you afraid that people might actually learn something and improve?

You can't really invoke Parkinson's Law of Triviality here, given that what we're talking about are basic programming features that affect every aspect of the language. That's the opposite of the Law of Triviality.

I look in the mirror and realize I won't be getting laid without being successful.

>>3674

i know that feel

>>3672

inspiration: noobody.org

Read about mathematical concepts, watch conference talks.

Occasionally a variation of this >>3674

I just have a vision in mind, and then go do it. I've never looked at anyone else's code. I've consistently ignored anything anyone says about "good" or "bad" languages, practices, anything. I just focus on my project, not worrying if I'm doing something in a "bad way" or any other distractions. That is all the "inspiration" I need.

3d space or 2d space? Do you actually mean lines or line segments?

If 2d space, just check the slope. They intersect if they aren't parallel.

In 3d space, calculate their closest points. They intersect if their closest point is equal.

>>3095

something something vectors.

https://www.cs.utah.edu/~jsnider/SeniorProj/BSP1/default.html

has some code that might help you, such as methods that determine wether a point is in front of or behind a plane.

>>3095

https://web.stanford.edu/~liszt90/acm/notebook.html#file8

Think of it like back in highschool algebra.

y=mx+b

if line 1 line 2

collision == true

>>3685

what about vertical lines?

it make a me feel gooot

>>3651

In C++, objects and structs are the same thing. struct and class are synonyms; it's valid C++ for a struct to have methods.

>>3639

There's a decent amount of research into that, the minimum required for turing completeness. Also a common theme in esolangs. Binary combinatory is pretty fuggin simple, le copy-paste from http://esolangs.org/wiki/Binary_combinatory_logic

Binary combinatory logic

Binary combinatory logic (BCL) is a complete formulation of combinatory logic (CL) using only the symbols 0 and 1, together with two term-rewriting rules. BCL has applications in the theory of program-size complexity (Kolmogorov complexity).

Contents

Definition

Syntax

<term> ::= 00 | 01 | 1 <term> <term>

Semantics

Rewriting rules for subterms of a given term (parsing from the left):

1100xy → x

11101xyz → 11xz1yz

where x, y, and z are arbitrary terms.

(Note, for example, that because parsing is from the left, 10000 is not a subterm of 11010000.)

The terms 00 and 01 correspond, respectively, to the K and S basis combinators of CL, and the "prefix 1" acts as a left parenthesis (which is sufficient for disambiguation in a CL expression).

There are four equivalent formulations of BCL, depending on the manner of encoding the triplet (left-parenthesis, K, S). These are (1, 00, 01) (as above), (1, 01, 00), (0, 10, 11), and (0, 11, 10).

>>3639

This isn't exactly what you're asking, but I prefer lambda calculus to a turing machine.

https://en.wikipedia.org/wiki/Lambda_calculus