Iterator pipelines and collection

The idea

Enter with closures, references, and vectors understood. An iterator produces a sequence of items as consumers request them. Adaptors such as filter and map describe work but are lazy: creating the pipeline alone does not process every element. A consumer such as collect, sum, or a for loop drives the iterator. Keep side effects out of transformations when a simple value calculation will do.

The item type depends on how iteration begins. iter borrows collection elements, whereas into_iter can consume an owned collection. copied turns references to Copy values into copied items. This makes a pipeline over integers easy to read without moving the original vector. Type annotations on collect tell Rust which result collection to build. Choose the pipeline by its data ownership as well as its arithmetic.

fn main(){
 let values=vec![1,4,7,8];
 let result:Vec<i32>=values.iter().copied().filter(|n|n%2==0).map(|n|n/2).collect();
 println!("{:?}",result);
}

[2, 4]

The consumer collects only even input values after halving them. iter and copied leave the original vector available.