the using keyword has many more uses. it can be used in a function scope rather than globally. it can be used to bring only the things you need to a scope rather than the whole namespace. void fn() { using std::cout; cout << "Hi!\n"; } Output Hi! void fn() { using v = std::ranges::views; using fmt::format; using std::vector; vector vec{1, 2, 3, 4, 5}; format(std::cout, "{}\n", vec | v::reverse); } Output {5, 4, 3, 2, 1}

when i write your second code on visual studio ,i get error in (ranges:: and format::) what's wrong ? i use GNU g++17

when i write your second code on visual studio ,i get error in (ranges:: and format::) what's wrong ? i use GNU g++17

You need to use a C++20 compiler. Try -std=c++20 or -std=c++2a as a command line option with g++ to see if it works

when i write your second code on visual studio ,i get error in (ranges:: and format::) what's wrong ? i use GNU g++17

std::format from C++20 is currently only supported in microsoft's standard library (and it doesn't have a function to directly output to an ostream), fmt requires fmtlib

You need to use a C++20 compiler. Try -std=c++20 or -std=c++2a as a command line option with g++ to see if it works

okay ,but in the codeforces, can i use this code in any problems ?

okay ,but in the codeforces, can i use this code in any problems ?

probably not. those were just examples for "alternatives to using namespace std"

i need pdf to learn html please help🙏

okay ,but in the codeforces, can i use this code in any problems ?

Codeforces is just an online platform. It depends on the compiler they use at the backend. So if their compiler supports the C++20 standard, (by default) then it should be able to build it.

Hi

i need pdf to learn html please help🙏

Me too pls

i want to learn c programming from basic

i want to learn c programming from basic

cool

Iie

i want to learn c programming from basic

cool

I also want

How to learn

maybe stay in this group

would give a sufficient understanding for C/C++

Does anyone have the C code for solar energy electiricty production simulation

#Puzzle #include <future> #include <atomic> std::atomic<int*> p {nullptr}; void f(){ p.store(new int{0}); } void g(){ while(!p.load()); } int main(){ std::async(std::launch::async, g); std::async(std::launch::async, f); } Why doesn't this program terminate?

the using keyword has many more uses. it can be used in a function scope rather than globally. it can be used to bring only the things you need to a scope rather than the whole namespace. void fn() { using std::cout; cout << "Hi!\n"; } Output Hi! void fn() { using v = std::ranges::views; using fmt::format; using std::vector; vector vec{1, 2, 3, 4, 5}; format(std::cout, "{}\n", vec | v::reverse); } Output {5, 4, 3, 2, 1}

nice.

#Puzzle #include <future> #include <atomic> std::atomic<int*> p {nullptr}; void f(){ p.store(new int{0}); } void g(){ while(!p.load()); } int main(){ std::async(std::launch::async, g); std::async(std::launch::async, f); } Why doesn't this program terminate?

Function f is blocked. But why?

#Puzzle #include <future> #include <atomic> std::atomic<int*> p {nullptr}; void f(){ p.store(new int{0}); } void g(){ while(!p.load()); } int main(){ std::async(std::launch::async, g); std::async(std::launch::async, f); } Why doesn't this program terminate?

can i give a hint?

can i give a hint?

Sure

#Puzzle #include <future> #include <atomic> std::atomic<int*> p {nullptr}; void f(){ p.store(new int{0}); } void g(){ while(!p.load()); } int main(){ std::async(std::launch::async, g); std::async(std::launch::async, f); } Why doesn't this program terminate?

Hint: the std::async() function template is marked [[nodiscard]] in C++20. Why?

hai guys i want your help

why this program give the wrong value?

can you delete this message, post the code either on wandbox.org or godbolt.org, and then share a link?

Hint: the std::async() function template is marked [[nodiscard]] in C++20. Why?

I love nodiscard so much tbf

It is the attribute of god

Hint: the std::async() function template is marked [[nodiscard]] in C++20. Why?

Let us see if people can figure out why that is a problem.

I love nodiscard so much tbf

True

can you delete this message, post the code either on wandbox.org or godbolt.org, and then share a link?

sorry but how i can share the link?..

Message it to one of the admins or to one of us. We will post it here for you.

True

That reminds me I need to add an optional sanitizer to my version of optional

sorry but how i can share the link?..

Ctrl+F on the website, search "Share"

for godbolt it's on the top right, for wandbox it's on the middle, above outputs (need to click "Run" once for it to show up)

That reminds me I need to add an optional sanitizer to my version of optional

Optional and Error values in C++ should be implemented the way Rust does it. We can easily implement something similar with the support available in C++20 but to get it to Rust level will require more support from the standardization committee.

for godbolt it's on the top right, for wandbox it's on the middle, above outputs (need to click "Run" once for it to show up)

I think people who joined the group recently are not allowed to post links

I think people who joined the group recently are not allowed to post links

oh right

Optional and Error values in C++ should be implemented the way Rust does it. We can easily implement something similar with the support available in C++20 but to get it to Rust level will require more support from the standardization committee.

Yep, that is close to what I do when I am not a lazy cunt. I need to add some stuff still though (I use my own "standard" library)

why this program give the wrong value?

Posting Code link on behalf of Alieya https://wandbox.org/permlink/82TzF6hPPfnD3ilo

Posting Code link on behalf of Alieya https://wandbox.org/permlink/82TzF6hPPfnD3ilo

Alieya Your code to convert the variables returns a value. Ideally these functions should take only one input and return an output. Your second input is practically useless because it is not used. Did you mean to pass it by reference and store the return value in it? You have to print the return values to see the output of your conversion functions. Why have you added blocks after the function call? You dont need them. And the call to each of your conversion function should be in a switch case depending on the value the user chose. The options you list should be in a while loop to allow the user to choose one of them. You dont care about the option chosen

Alieya Your code to convert the variables returns a value. Ideally these functions should take only one input and return an output. Your second input is practically useless because it is not used. Did you mean to pass it by reference and store the return value in it? You have to print the return values to see the output of your conversion functions. Why have you added blocks after the function call? You dont need them. And the call to each of your conversion function should be in a switch case depending on the value the user chose. The options you list should be in a while loop to allow the user to choose one of them. You dont care about the option chosen

ouh..i see.i put the blocks after function call because it say error there

so i put it..and have semicolon

ouh..i see.i put the blocks after function call because it say error there

You dont need the blocks. You need the semicolon after the function call statement but.

You dont need the blocks. You need the semicolon after the function call statement but.

ouhh i get it..thanks..👍👍

Yep, that is close to what I do when I am not a lazy cunt. I need to add some stuff still though (I use my own "standard" library)

Do you have a github link? I want to see why you need to reinvent the wheel.

Do you have a github link? I want to see why you need to reinvent the wheel.

I need to reinvent the wheel because I often work in kernel space

Do you have a github link? I want to see why you need to reinvent the wheel.

https://git.nekoit.xyz/Archivist

I need to reinvent the wheel because I often work in kernel space

This means that my lib is actually freestanding C++20

I need to reinvent the wheel because I often work in kernel space

Aah ok. Are you writing your own kernel? Linux has an implementation for most of the kernel data structures you might need in the kernel.

Any group for finding 3d artist

Aah ok. Are you writing your own kernel? Linux has an implementation for most of the kernel data structures you might need in the kernel.

Yeah, let's not speak my mind about those implementations and Linux coding style, nor about their portability to other kernels

Or the GPL 2

Yeah, let's not speak my mind about those implementations and Linux coding style, nor about their portability to other kernels

Hahaha.

Hahaha.

I apologize but I remember that time when I received death threats for saying that rms was a politician and not a dev

So the only open source communities I comment deeply about would be the OpenBSD and 9front commus

Aah ok. Are you writing your own kernel? Linux has an implementation for most of the kernel data structures you might need in the kernel.

If my code is hard to read on the git, blame whatever buggy CSS preprocessor makes the theme go drunk when not connected

I need to reinvent the wheel because I often work in kernel space

Nice. I just checked your vector and flat tree code just to see how exception safe it is. At a superficial level, it looks like you have all the bases covered. I will bookmark it and see if there is something I can contribute to. If yes, I will touch base.

Nice. I just checked your vector and flat tree code just to see how exception safe it is. At a superficial level, it looks like you have all the bases covered. I will bookmark it and see if there is something I can contribute to. If yes, I will touch base.

I try to work steadily and test things but I have some basic stuff (mostly, when I need something I implement it)

I try to work steadily and test things but I have some basic stuff (mostly, when I need something I implement it)

What exactly are you working on Ludovic? Your own kernel or on the linux kernel?

What exactly are you working on Ludovic? Your own kernel or on the linux kernel?

Kernel modules for the network file system I am making

(as well as the similar drivers for Windows)

Kernel modules for the network file system I am making

Linux kernel or custom?

Linux kernel or custom?

Linux, OpenBSD and Windows

Linux, OpenBSD and Windows

Interesting 👍👍

#Puzzle #include <future> #include <atomic> std::atomic<int*> p {nullptr}; void f(){ p.store(new int{0}); } void g(){ while(!p.load()); } int main(){ std::async(std::launch::async, g); std::async(std::launch::async, f); } Why doesn't this program terminate?

Ok. The destructor of future waits forever and blocks the main thread. The f thread is never created. Defer the destructor can solve it. Interesting. [[nodiscard]] is useful to prevent these problems.

Ok. The destructor of future waits forever and blocks the main thread. The f thread is never created. Defer the destructor can solve it. Interesting. [[nodiscard]] is useful to prevent these problems.

Yup. That is correct 👍👍👌

hello

can we multiply 3 matric together?

can we multiply 3 matric together?

If the dimensions of the 3 matrices are mxn, nxp, pxq then yes.

mxn, nxp, pxq meaning?

mxn, nxp, pxq meaning?

Dimensions of the matrices. m rows n columns and so on

Write a complete C++ program which can multiply three matrices. Your program need to read matrix A , Matrix B, and Matrix C from data file. The size of all the matrices must be at least 3 x 3 Your program must also store the result into result file.

above are the question

Write a complete C++ program which can multiply three matrices. Your program need to read matrix A , Matrix B, and Matrix C from data file. The size of all the matrices must be at least 3 x 3 Your program must also store the result into result file.

Yup. So go ahead and write your program.

im done but i can' do the 3rd matric

You mean you multiplied the first 2 matrices?

#include <iostream> #include <fstream> using namespace std; int main() { // declaring array variables a, b to hold input matrices // declaring array variable mult to hold the result matrix multiplication int a[100][100], b[100][100], mult[100][100]; // declaring variables r1, c1 to hold the dimensions of matrix a // declaring variables r2, c2 to hold the dimensions of matrix b int r1, c1, r2, c2; // creating an instance of ifstream class to read data from file ifstream infile; // open matrix.dat file to read data of matrices a and b infile.open("matrix.dat"); /* check if matrix.dat file is opened correctly or not if there any error while opening file, report the information to user and stop execution of program */ if (!infile) { cout << " Cannot open the input file."; return 0; } // read the dimensions of matrix a from file infile >> r1 >> c1 ; // read r1 x c1 matrix data from file and store it into array a for(int i = 0; i < r1; i++) for(int j = 0; j < c1; j++) infile >> a[i][j]; // display data of matrix a read from file cout << endl << " Data of Matrix A is: " << endl; for(int i = 0; i < r1; ++i) { for(int j = 0; j < c1; ++j) cout << "\t" << a[i][j]; cout << endl; } // read the dimensions of matrix b from file infile >> r2 >> c2 ; // read r2 x c2 matrix data from file and store it into array b for(int i = 0; i < r2; i++) for(int j = 0; j < c2; j++) infile >> b[i][j]; // display data of matrix b read from file cout << endl << " Data of Matrix B is: " << endl; for(int i = 0; i < r2; i++) { for(int j = 0; j < c2; j++) cout << "\t" << b[i][j]; cout << endl; } /* checking whether multiplication of the matrix can be done If number of columns (c1) of matrix a in not equal to number of rows (r2) of matrix b, then then multiplication of matrix cannot be done */ if (c1 != r2) { cout << " Error! Matrix Multiplication cannot performed"; return 0; } // continuing with matrix multiplication // Initializing elements of matrix mult to 0. for(int i = 0; i < r1; i++) for(int j = 0; j < c2; j++) mult[i][j] = 0; // Multiplying matrix a and b and storing in array mult. for(int i = 0; i < r1; i++) for(int j = 0; j < c2; j++) for(int k = 0; k < c1; k++) mult[i][j] += a[i][k] * b[k][j]; // Displaying the result of matrix multiplication cout << endl << " The result of Matrix Multiplication is : " << endl; for(int i = 0; i < r1; i++) { for(int j = 0; j < c2; j++) cout << "\t" << mult[i][j]; cout << endl; } // writing result of matrix multiplication into matrix.res file // creating an instance of ofstream class to write data into file ofstream outfile; // open matrix.res file to write data of matrix mult into file outfile.open("matrix.res"); /* check if matrix.res file is opened correctly or not if there any error while opening file, report the information to user and stop execution of program */ if (!outfile) { cout << " Cannot open the output file."; return 0; } // otherwise, write mult matrix data into file for(int i = 0; i < r1; i++) { for(int j = 0; j < c2; j++) outfile << mult[i][j] << " "; outfile << "\n"; } return 0; }

i got provided the source code can you help me to check?