How is the connection between the keyword 'in' and collections in C implemented?

In the C language, there is no in keyword like in Python or other languages, where it is used to check for membership in a collection.

If we talk about working with collections in the context of Android (Java/Kotlin), then in is an operator that checks if an element is contained in a collection. In C, there is no such construct, and membership checking is implemented manually.

For example, to check if an element exists in an array in C, you need to write a loop:

#include <stdbool.h>

bool contains(int *arr, int size, int value) {
    for (int i = 0; i < size; i++) {
        if (arr[i] == value) {
            return true;
        }
    }
    return false;
}

Thus, in C there is no direct relation between the in keyword and collections, as the in keyword itself does not exist in the language. All operations with collections are implemented through loops and functions.