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Hello.
I have a simple code in MS Visual Studio with C++ that aims to enter values into a two-dimensional matrix and display the entered values on the screen.
When I write exactly the same code in DevC++, it works but in MS Visual Studio, it gives the error "C2131 expression did not evaluate to a constant" on the line I marked as LINE 39.
I'm guessing it's an issue with the compiler or C++ standards but I couldn't find a solution for this code.
How can I solve this problem? How can I make the code I wrote work?
Thank you in advance to everyone who takes the time to help.
#include <iostream>
#include <stdio.h>
using namespace std;
int main() {
int R, C;
cout << "Enter the value of the row: "; cin >> R;
cout << "Enter the value of the column: "; cin >> C;
cout << endl;
int a[R][C]; // >>>>>>>>>>>>>>>> LINE 39, C2131 Error <<<<<<<<<<<<<<<
for (int i = 0; i < R; i++) {
for (int j = 0; j < C; j++) {
cout << i + 1 << ". row, " << j + 1 << ". column: "; cin >> a[i][j];
}
cout << endl;
}
cout << endl << endl;
for (int i = 0; i < R; i++) {
for (int j = 0; j < C; j++) {
cout << "\t" << a[i][j];
}
cout << endl;
}
return 0;
}
A high-level, general-purpose programming language, created as an extension of the C programming language, that has object-oriented, generic, and functional features in addition to facilities for low-level memory manipulation.
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Answer accepted by question author
You are using a compiler that offers a non-standard additional feature: Variable-Length Arrays.
In Visual Studio, try an alternative:
//int a[R][C]; // >>>>>>>>>>>>>>>> LINE 39, C2131 Error <<<<<<<<<<<<<<<
vector<vector<int>> a( R );
for( auto& r : a ) r.resize( C );
Also add #include <vector>.
However, there are other solutions.
Hello, first of all, I would like to thank you; the problem was solved and the code became working.
In order not to disturb you again and again, how can I reach the necessary current C, C++ and C# standards and do you know educational resources where I can learn them?
Thank you again, Viorel
Instead of simply defining an array, entering the values directly and simply getting the result, why are there slightly more complex methods? Security issues, speed issues or something else?
The problem is solved but if you want to share, what would be other solutions to this code?
Instead of simply defining an array, entering the values directly and simply getting the result, why are there slightly more complex methods? Security issues, speed issues or something else?
The problem is solved but if you want to share, what would be other solutions to this code?
@Isaac GM Following adaptation of your posted code shows another way of dynamically allocating and using a multidimensional array. It is not as elegant or as safe as using vectors but it does demonstrate how the memory address of an array element can be determined. There are many such examples on the internet if you search for "C Multidimensional Array".
#include <iostream>
#include <stdio.h>
using namespace std;
int main() {
int a[3][2]; // For comparison with dynamically allocated multidimensional array
int R{ 3 }, C{ 2 }; // assume that rows and columns were provided by user interaction
int* pArray = new int[R*C];
for (int i = 0; i < R; i++) {
for (int j = 0; j < C; j++) {
int* pElement = pArray + (i * C) + j;
cout << i + 1 << ". row, " << j + 1 << ". column: ";
cin >> *pElement;
a[i][j] = *pElement; // insert same value into static
}
cout << endl;
}
cout << endl << endl;
cout << "Content of static multidimensional array\n";
for (int i = 0; i < R; i++) {
for (int j = 0; j < C; j++) {
cout << "\t" << a[i][j];
}
cout << endl;
}
cout << "Content of dynamically allocated multidimensional array\n";
for (int i = 0; i < R; i++) {
for (int j = 0; j < C; j++) {
cout << "\t" << *(pArray + (i * C) + j);
}
cout << endl;
}
delete[] pArray;
return 0;
}