Why is this wrong (C++)??

Question

#include <iostream>
#include <string.h>
using namespace std;

int main() {

char msg[];
cin >> msg;

strrev(msg);

cout << msg;

return 0;
}

Answer 1

You need to say how long your array is when you declare it.

Answer 2

You should get accustomed with the C++ specific string type.

If we want to make your code work as it is, this will work:

#include <iostream>
#include <algorithm>
using namespace std;

int main() {
char msg[10];
cin >> msg;
int i=-1;
while(msg[++i]);
reverse(msg, &msg[i]);
cout << msg;
return 0;
}

EDIT: Downvote? Hmm...
EDIT: Two already... LOL!

Answer 3

For the strrev() part, the function is not a standard function, so it is not mandatory for compilers to support it.
SoloLearn recently shifted from a Windows environment to Linux and updated their compiler, that's probably why it is not supported here anymore:

https://stackoverflow.com/questions/8534274/is-the-strrev-function-not-available-in-linux

Also see the excellent answer to a similar question in this thread:

https://www.sololearn.com/discuss/2100807/?ref=app

Answer 4

Well

Answer 5

The "strrev" doesnt work either

Answer 6

Lol😂😂 i understand. But sometimes we need to cheat. Otherwise we will not have what we really want. It's too difficult to do this by that way Bilbo Baggins

Answer 7

strrev is not standard function

Answer 8

well, I haven't seen that library yet, so....

Answer 9

I just wanted to know why it doesn't work, and I still don't understand why there is no such method if I just saw it.

Answer 10

As Shadow pointed out, strrev() is not present in GCC for Linux.
As HonFu pointed out, you can use reverse() after including <algorithm>: for example
reverse(msg, msg+strlen(msg))
And you cannot declare char msg[] without a size

Answer 11

That's cheating 😄

Answer 12

Why is getline cheating? *looks around naively serious*

Answer 13

You are right, HonFu, std::getline() is perfect in C++ language, maybe the best way to get strings from input...
But it requires std::string.

In the current thread I was just (academically) curious to see if C++ had changed the way in which a character array (in the C acception) can be defined.
And I am afraid that the answer is no: a character array must always be defined along with a fixed size.
This is eventually the reason to prefer std::string, which is dynamic.

By the way, in Python a character array (string) is even more restrictive: it is immutable, not just fixed size.

Answer 14

Flayer
unfortunately it does not work...

./Playground/file0.cpp: In function 'int main()':
./Playground/file0.cpp:10:12: error: expected primary-expression before 'char'
10 | cin >> char msg[];
| ^~~~

Answer 15

Bilbo Baggins I works in c#
But try to do something like
cin >> anyvar
char[] anyarr = anyvar.ToCharArray()
I did half of it in c# but try to translate it

Answer 16

Hello have you tried to use a String with a getline() function instead?

Answer 17

#include<iostream.h>
This while this is wrong

Answer 18

Hlo

Answer 19

eed

Answer 20

cin >> char msg[]
It will find the size it self