How does List::insert work with arrays

Question

I am on youtube looking over tutorials. One had a block of code using the list library as such:

int arr1[5]{ 1,2,3,4,5 };
list<int> list1;
list1.insert(list1.begin(), arr1, arr1 + 5);

My question is, how can one use an array like this? Last I checked, arr1 is an array not a pointer that you use to loop through elements. How does the insert function work?

In most cases, arrays are automatically converted to pointers to their first elements. It happens here too. — HolyBlackCat, May 03 '20 at 23:21
This is commonly known as "decay". See https://stackoverflow.com/questions/1461432/what-is-array-to-pointer-decay — Sebastian Hoffmann, May 04 '20 at 00:01

score 2 · Accepted Answer · answered May 03 '20 at 23:33

When an array is used by name, it's name references to first element of the array. For an array arr whenever you say arr[x], [] is defined in terms of pointers. It means start at a pointer referencing arr and move x steps ahead. A size of each step is the sizeof datatype your array is made up of. Thus,arr[x] can also be written as *(arr + x), dereferencing the pointer after x steps.

Now speaking of your list insertion, it means copy all the elements between pointers arr and arr + 5 to the list.

thanks for this! Clarifies stuff my prof skipped over in class. Damn nobody told me this — edo101, May 03 '20 at 23:48

Alejandro De Cicco · Answer 2 · 2020-05-03T23:23:13.170

0

arr1 can be used as a pointer to the beginning of the array, because it gets converted automatically.

edited May 03 '20 at 23:23

answered May 03 '20 at 23:21

Alejandro De Cicco

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2 Answers2

How does List::insert work with arrays