Initializing a local one dimension array in c

[DiptenduDas]

Want to initialize a local one dimensional array. How can I do the same without a loop?
Found from some links that
int iArrayValue[25]={0};
will initialize all the elements to ZERO. Is it?
If yes then can we write below code to initialize the elements to a non-ZERO value?

int iArrayValue[25]={4};

Do we have some other way to initialize an array to a non-ZERO value?
memset can help us to initialize the element to ZERO.

[Cubbi]

Do we have some other way to initialize an array to a non-ZERO value?

std::vector<int> iArrayValue(25, 4);

[andywestken]

int iArrayValue[25]={4};

initializes the 0th elem to 4 and the rest to 0

I'm not sure it's possible without some sort of loop. Even = {0} is (usually, see PS) using a loop behind the scenes, so I assume you mean without using an explicit loop?

So if you have some sort of aversion to vectors, you can use the std::fill algorithm?

std::fill
http://www.cplusplus.com/reference/algorithm/fill/

Andy

PS I think for very small arrays, the compiler will just set the memory to zero directly (by treating it as an int or whatever.) But under the debugger you can see that this code (for not so small arrays)

int iArrayValue[1024]={0};

get converted to a call to

memset(iArrayValue, 0, sizeof(iArrayValue));

(at least with the Visual C++ compiler.)

[DiptenduDas]

Thnx Cubbi and andy!!!

Actually I wanted to know how
int iArrayValue[1024]={0};
is implemented internally.

If int iArrayValue[1024]={0}; is internally converted to memset(iArrayValue, 0, sizeof(iArrayValue));

then why int iArrayValue[1024]={4}; is not converted to memset(iArrayValue, 4, sizeof(iArrayValue));

[z05DSL3A]

int iArrayValue[1024]={4}; only meant to set the first element to 4.

#include <iostream>

int main()
{
    const int arr_size = 10;
    int arr[arr_size] = {1,2,3}; // set the first three elements to 1,2,3 and zero the rest
    int arr2[arr_size] = {}; // zero all element [C++]
    
    for(int count = 0; count < arr_size; count++)
    {
        std::cout << arr[count] << " " << arr2[count] << std::endl;
    }
}

[vlad from moscow]

In C there are two ways to initialize all elements of an array of a fundamental type. Either you use a loop or you call standard function memset. Without these approaches you can only initialize all elements to zeroes when you are defining an array

[DiptenduDas]

Thnx

Grey Wolf

for your input.
But I wanted to know how to initialize an array to a constant value without using an explicit loop.
Is there anyway out? For this I want to know how internally below statement
int arr2[arr_size] = {}; // zero all element [C++]
is being handled, so that a similar way can be thought of.


My problem is that I need to reset an array at runtime to a non-ZERO +ve value. Currently I am doing this in a for loop. But searching for a better one.

[z05DSL3A]

I was addressing

then why int iArrayValue[1024]={4}; is not converted to memset(iArrayValue, 4, sizeof(iArrayValue));

memset will not work for you unless you just want any non-zero int. If you want to set each element to say 4, you will need to use a loop.