Linear searching is a fancy name for something that we do in almost every program and our everyday lives: going through a collection of items to find the first match. There is no need for any preprocessing or similar steps; the collection can be used as-is, which means that standard libraries commonly provide a generic implementation already. In Rust's case, the iterator trait offers this feature with functions called position() (or rposition()), find(), filter(), or even any(). fold() can also be used to find the thing you are looking for. The following is a diagram of the process:
Fundamentally, however, it's a loop over each item that either exits or collects all items where a predicate (an evaluation function that takes in an item of a type to return a Boolean value) matches:
pub fn linear_search<T: Eq + Clone>(haystack: &[T], needle: &T) -> Option<usize> {
for (i, h) in haystack.iter().enumerate() {
if h.eq(needle) {
...
