otherwise you get UB and potential segfault

It is obviously something like hackerrank task, input validation can be omitted there

#include <iostream> int main() { int N; std::cin >> N; int arr[1000]; for( int i = 0; i <= N; i++){ std::cin >> arr[i]; } for ( int i = 0; i<= N; i++){ std::cout << arr [i] << " "; } }

What about int arr[N]; instead of int arr[1000];? Is it allowed?

What about int arr[N]; instead of int arr[1000];? Is it allowed?

in this case no, N should be macro or const

in this case no, N should be macro or const

I tried it and it showed no problems. But I still don't like that some books forbid it.

so the teacher prompted me that i can in arr[1000];

What about int arr[N]; instead of int arr[1000];? Is it allowed?

You can do like this also : int array1[]

haw i can writ in const form?

so write up to 1000?

haw i can writ in const form?

constexpr int N = 1000;

I tried it and it showed no problems. But I still don't like that some books forbid it.

const is not forbidden.

#include <iostream> int main() { int N; std::cin >> N; const int arr =1000;

that's right?

ok

natural number N (N ≤ 1000) at the input, then a sequence of whole N elements.

=?

Or<=?

<=

for( int i = 0; i < N; i++){ std::cin >> arr[i]; } for ( int i = 0; i< N; i++){ std::cout << arr [i] << " "; } }

I seem to have errors here too

I will show the task again

#include <iostream> int main() { int N; std::cin >> N; const int arr =1000; for( int i = 0; i < N; i++){ std::cin >> arr[i]; } for ( int i = 0; i< N; i++){ std::cout << arr [i] << " "; } }

Write a program that gets a natural number N (N ≤ 1000) at the input, then a sequence of whole N elements. As a result, the program must display the sequence in reverse order. Use array to solve the problem

arr should be array, not a number

😞

I don’t understand

#include <iostream> int main() { int N; std::cin >> N; int arr[1000]; for( int i = 0; i <= N; i++){ std::cin >> arr[i]; } for ( int i = 0; i<= N; i++){ std::cout << arr [i] << " "; } }

Here you had a correct syntax for your arr declaration

Use it in your latest example

but the compiler says something is wrong

but the compiler says something is wrong

What does it say?

Of course wrong. How do you expect it to deal with arr[i] when arr is an integer?

 clang++-7 -pthread -std=c++17 -o main main.cpp main.cpp:10:18: error: subscripted value is not an array, pointer, or vector std::cin >> arr[i]; ~~~^~ main.cpp:13:21: error: subscripted value is not an array, pointer, or vector std::cout << arr [i] << " "; ~~~ ^~ 2 errors generated. compiler exit status 1 

What about int arr[N]; instead of int arr[1000];? Is it allowed?

Yes ,by using preprocessing

whot i must to du?

 clang++-7 -pthread -std=c++17 -o main main.cpp main.cpp:10:18: error: subscripted value is not an array, pointer, or vector std::cin >> arr[i]; ~~~^~ main.cpp:13:21: error: subscripted value is not an array, pointer, or vector std::cout << arr [i] << " "; ~~~ ^~ 2 errors generated. compiler exit status 1 

Well, yes, it basically what Artom and E B said

 clang++-7 -pthread -std=c++17 -o main main.cpp main.cpp:10:18: error: subscripted value is not an array, pointer, or vector std::cin >> arr[i]; ~~~^~ main.cpp:13:21: error: subscripted value is not an array, pointer, or vector std::cout << arr [i] << " "; ~~~ ^~ 2 errors generated. compiler exit status 1 

Declare arr as an array, I pointed out the code where it was correct

Yes ,by using preprocessing

N is known only at runtime, as I understand

What about int arr[N]; instead of int arr[1000];? Is it allowed?

We can define like this #define N 1000

We can define like this #define N 1000

Don't teach them this prohibited magic :D

Don't teach them this prohibited magic :D

It's possible yar

We can define like this #define N 1000

I know that. I meant int N; cin>>N; int arr [N]; The point is that the compiler doesn't know the size of the array the moment of compiling.

Ok

I know that. I meant int N; cin>>N; int arr [N]; The point is that the compiler doesn't know the size of the array the moment of compiling.

Some books say it isn't allowed. But when I tried it, it succeeded.

Some books say it isn't allowed. But when I tried it, it succeeded.

what compiler did you use?

g++ 4.9.2 2014

well wait.. it does compile, why?

well wait.. it does compile, why?

Sometimes the problem is that it succeeds when we don't suppose it to.

Sometimes the problem is that it succeeds when we don't suppose it to.

OK, my colleagues told me that gcc supports VLA extension (variable-length arrays) that as I understood is part of C standart (C99?) but not part of any C++ standard. So in other words it's only a gcc feature in context of C++.

running ++i; on your x86 hardware is not atomic

atomic instructions add assembly code that tell cpu how to order and maintain cache consistency someone new to programming should not pay much attention to this yet. it is complicated. most languages do not expose this level of detail

yes

first outcome: 1087851 second outcome: 1031545 third outcome: 1112568 forth outcome: 1071384 fifth outcome: 1155180

if there threads are running in different cores and three cores have the value x in caches for the core then in an indeterminate way they will be incrementing x in that cache when you do mutual exclusion or atomics the processor well make sure that the cache values of x values are synchronized it doesn't matter if heap or stack when program starts the operating system gives it some stack when a function or thread starts that function or thread is given some stack also also when a program starts the runtime makes a call to the operating system and asks for a chunk of memory which this run time makes into a heap the runtime will ask the os for more memory or return some as needed. when the program and that memory was returned to the operating system malloc on Linux first try to do mutual exclusion in user space, see futex, which is faster and then revert to mutual exclusion in the kernel which is slower you can manage your own heap if you want also. the Linux call is sbrk for the chunk of memory

that is true the different models exist for different processors, . Intel x86 naturally maintains a lot of cache consistency where is arm powerpc do not

I would have to look it up but there's some load in the stores that are cache consistent 4 integral types herb Sutter did a great talk on this. the video is up on YouTube and channel 9

thank you

What is the significance of modulo operator in the Caesar encryption algorithm?

And even before that what is the need of remainder? What good are they?

This is cool but hard to grasp.

Who has ever used Gtk?!

In C programing

i need a information about c++

especially where you can find various tasks

i need a information about c++

Google.com

Seriously

Seriously

He is serious

especially where you can find various tasks

c++ books usually include exercise after each chapter

ok. for wile prefix postfix const int?

about this

https://isocpp.org/wiki/faq/const-correctness

I need tasks and their solutions

Task about what? About const? I cant imagine such tasks

If you want to be professional, read Programming principles and practice by Bjarne Stroustrup. Otherwise, I highly recommend you to begin with C++ without fear by Brian Overland.

Thank you so much

What does it say?

you know howe mach I am tride It does not work you can help to write this code?

good article. it mentions: for aligned x86 accesses, it is not necessary to consider write/write pairs as competing i will try to find the sutter presentation and seen if i got it worng

how can i solve dining philosopher's problem in c++

do i have to make 5 programs for eac philosopher?

each program for each philosopher*

?

but do I have to create 1 different program for each philosopher?

is there any easier way?

yes, do i need a saparate running process?