Structure of assigning values to an array member in C++

Ken H

11y1.3k

Hello friend,

My code is as follows(In bold-part question):
#include "stdafx.h"
#include
using namespace std;;
#define MAX_ARR_SIZE 10
typedef int ElementType;
typedef struct
{
ElementType arr[MAX_ARR_SIZE];
int length;
}MyStr;
void outputE(MyStr *ms){

int i;

for (i = 0; i < ms->length; i++) cout << ms->arr[i] << ",";

cout << ms->arr[i] << endl;

}
int _tmain(int argc, _TCHAR* argv[]){

MyStr ms;

ms.length = MAX_ARR_SIZE;

// try a one-time assignment. but a compiler error has occurred(In addition to each assignment, but are there other ways?).

ms.arr[MAX_ARR_SIZE] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

outputE(&ms);

system("pause");

return 0;

}
Thanks.

2 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes11y ago
Accepted answer
Unfortunately, you can only use 'list initialization' to initialize local arrays at the same time as they're declared. So this would work:

ElementType et[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

and so would this:

ElementType et[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

as the compiler would infer the size of the array to be 10.

However, this wouldn't work:

ElementType et[10];
et = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; // not a declaration

So you'll need to use a loop to assign values to the struct member, arr:

for(int i = 0; i < ms.length; i++) ms.arr[i] = i + 1;

Incidentally, I noticed a mistake in your output() method:

void outputE(MyStr *ms){

int i;

for (i = 0; i < ms->length - 1; i++) cout << ms->arr[i] << ",";

cout << ms->arr[i] << endl;

}
Ken H11y ago
Thank you for your explanation,Vulpes :)