I specified the sizes of the arrays so char myCharArr[4] = "hello world"; assigns only the first 4 chars without '\0'. Then memcpy copies this data "as is" to data.shortArr. So this array has only this 4 chars. someGarbage is an arrays of 16 chars, when I assign "some garbage" there, it sets first 12 chars to represent the symbols of the string, then sets 13th char to zero ('\0'), the last three chars probably left as zero (not sure if in C they are initialized or not to zero), but we don't care at all here about these last three chars. When I memcpy the someGarbage array I copy all 16 chars "as is". What I wanted to show, that if you print your array of 4 chars withour '\0' at the end, then it's matter of luck whether it will be printed correctly or not (as in klimi's example there can be non-zero memory after your array on the stack and then it will interpret memory as part of your string until it find a zero byte). You don't want to rely on something that works by luck.

I specified the sizes of the arrays so char myCharArr[4] = "hello world"; assigns only the first 4 chars without '\0'. Then memcpy copies this data "as is" to data.shortArr. So this array has only this 4 chars. someGarbage is an arrays of 16 chars, when I assign "some garbage" there, it sets first 12 chars to represent the symbols of the string, then sets 13th char to zero ('\0'), the last three chars probably left as zero (not sure if in C they are initialized or not to zero), but we don't care at all here about these last three chars. When I memcpy the someGarbage array I copy all 16 chars "as is". What I wanted to show, that if you print your array of 4 chars withour '\0' at the end, then it's matter of luck whether it will be printed correctly or not (as in klimi's example there can be non-zero memory after your array on the stack and then it will interpret memory as part of your string until it find a zero byte). You don't want to rely on something that works by luck.

first time hearing matter of luck in computer science :)

then it must be the job of the compiler to make sure memory is properly assigned, right?

Well, bad news, a lot of responsibility of not getting into UB is on you as a programmer if you write in C or C++ :)

Well, bad news, a lot of responsibility of not getting into UB is on you as a programmer if you write in C or C++ :)

In C++ it's kind of better because there are more high level concepts that can check things for you, but there can be overhead (runtime, compile time, or increase of complexity) of that checks (bearable, in my opinion).

then, those people who wrote those compilers must have gone through a lot of UB

#include <cstdlib> #include <iostream> #include <ostream> int main() { int rank; std::cin >> rank; int diagonal1{0}, diagonal2{0}; int matrix[rank][rank]; // for diagonal 1 and also for inputting matrix for (int i = 1; i <= rank; i++) { for (int j = 1; j <= rank; j++) { std::cin >> matrix[i][j]; if (i == j) { diagonal1 = diagonal1 + matrix[i][j]; } } } // for diagonal 2 int i{1}, j{rank}; while (i <= rank) { diagonal2 = diagonal2 + matrix[i][j]; j--; i++; } // std::cout << "Diagonal1 : " << diagonal1 << "\n"; // std::cout << "Diagonal2 : " << diagonal2 << "\n"; std::cout << abs(diagonal1 - diagonal2); return 0; }

#include <cstdlib> #include <iostream> #include <ostream> int main() { int rank; std::cin >> rank; int diagonal1{0}, diagonal2{0}; int matrix[rank][rank]; // for diagonal 1 and also for inputting matrix for (int i = 1; i <= rank; i++) { for (int j = 1; j <= rank; j++) { std::cin >> matrix[i][j]; if (i == j) { diagonal1 = diagonal1 + matrix[i][j]; } } } // for diagonal 2 int i{1}, j{rank}; while (i <= rank) { diagonal2 = diagonal2 + matrix[i][j]; j--; i++; } // std::cout << "Diagonal1 : " << diagonal1 << "\n"; // std::cout << "Diagonal2 : " << diagonal2 << "\n"; std::cout << abs(diagonal1 - diagonal2); return 0; }

You iterate from 1 to rank, you need to iterate from 0 to rank-1 for (int i = 0; i < rank; ++i) or substract 1 to get the index otherwise you get out of bounds of your arrays

But I didn't understood that.... My code should also work fine naa ? As it is working fine in my pc

Reading/writing out of bounds of an array is undefined behavior (we just descussed it a few messages above). Try running locally under the debugger and look at the values in your array when you assign the last values. I guess it either will also crash under debug or will show you that you overwrite values from the neighboring memory (e.g. values of the next array). But maybe it's a bad advise, again because UB don't need to be investigated if we know that it's UB. But I think it will be interesting for you to see what happens.

std::map<std::string,std::map<customtype1,customtype2>> xx ;

use method pair

Hi guys, I have a question. When are multidimensional arrays useful? In which kind of situation do you need more than 2 dimensions?

3 dimension table, 3D graphics.

"string" in C is just a char*. Char* doesn't copy anything. It stores address.

Hey can someone help me with my code?

Okay so let me send you the code?

I keep getting an error around the get line function

#include<iostream> #include<fstream> #include<string> #include<cmath> using namespace std; int main() { char x; float y; string z; cout<<"Enter the acronym"<<endl; cin>>z; cout<<"Enter the first number\n"; while(std::getline(cin,x)); { if(z=="sin(x)") { cout<<sin(x); } else if(z=="cos(x)") { cout<<cos(x); } else if(z=="tan(x)") { cout<<tan(x); } } return 0; }

Don't use char as argument to getline.

#include<iostream> #include<fstream> #include<string> #include<cmath> using namespace std; int main() { char x; float y; string z; cout<<"Enter the acronym"<<endl; cin>>z; cout<<"Enter the first number\n"; while(std::getline(cin,x)); { if(z=="sin(x)") { cout<<sin(x); } else if(z=="cos(x)") { cout<<cos(x); } else if(z=="tan(x)") { cout<<tan(x); } } return 0; }

open docs

I'm sorry what?

I'm sorry what?

So You are coding, but don't use documentation?

Oh I do. I save it as a file not a document. The file directly goes to the code in my compiler

Lol wtf

Don't send me anything

open docs

What does this mean then?

Why don't people just drop the question instead of saying "Can someone help with my code?"?

cppreference.com

Oh I do. I save it as a file not a document. The file directly goes to the code in my compiler

😂

What? Is there a problem?

nothing, I just like your joke

I'm not

ohh kk, I thought you were joking