When you initialize an array, you can assign multiple values to it in one spot:
int array [] = {1,3,34,5,6};
... but what if the array is already initialized and I want to completely replace the values of the elements in that array in one line:
int array [] = {1,3,34,5,6};
array [] = {34,2,4,5,6};
This doesn't seem to work. Is there a way to do so?
There is a difference between initialization and assignment. What you want to do is not initialization, but assignment. But such assignment to array is not possible in C++.
Here is what you can do:
#include <algorithm>
int array [] = {1,3,34,5,6};
int newarr [] = {34,2,4,5,6};
std::ranges::copy(newarr, array); // C++20
// or
std::copy(std::begin(newarr), std::end(newarr), std::begin(array)); // C++11
// or
std::copy(newarr, newarr + 5, array); // C++03
In C++11, you can also do this:
std::vector<int> array = {1,3,34,5,6};
array = {34,2,4,5,6};
Of course, if you choose to use std::vector instead of raw array.
std::copy(std::begin(newarr), std::end(newarr), std::begin(array)); would be better, wouldn't it?
std::array instead of std::vector when it's fixed size.
You have to replace the values one by one such as in a for-loop or copying another array over another such as using memcpy(..) or std::copy
e.g.
for (int i = 0; i < arrayLength; i++) {
array[i] = newValue[i];
}
Take care to ensure proper bounds-checking and any other checking that needs to occur to prevent an out of bounds problem.
I made a little template function to conveniently assign values to a raw pointer.
template <typename T, typename U>
void set_array(T* array, U x) {
*array = x;
}
template <typename T, typename U, typename... V>
void set_array(T* array, U x, V... y) {
*array = x;
set_array(array + 1, y...);
}
An example is:
int main() {
int64_t array[10] = {};
set_array(array, 11, 12, 13, 14, 15, 16);
for (int i = 0; i < sizeof(array) / sizeof(array[0]); ++i) {
std::cout << array[i] << ", ";
}
}
...and it should print:
11, 12, 13, 14, 15, 16, 0, 0, 0, 0,
const static int newvals[] = {34,2,4,5,6};
std::copy(newvals, newvals+sizeof(newvals)/sizeof(newvals[0]), array);
You could use a range based for loop like this:
int array[] = { 1, 3, 34, 5, 6 };
int count = 0;
for (int num : { 34, 2, 4, 5, 6 })
{
array[count++] = num;
}
