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This adds strictly more information to the source files and reduces the need for customized tooling to render the book. (While this should not change the output of _rustbook_, it is very useful when rendering the sources with external tools like Pandoc.)
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% Vectors
A ‘vector’ is a dynamic or ‘growable’ array, implemented as the standard
library type Vec<T>. The T means that we can have vectors
of any type (see the chapter on generics for more).
Vectors always allocate their data on the heap.
You can create them with the vec! macro:
let v = vec![1, 2, 3, 4, 5]; // v: Vec<i32>
(Notice that unlike the println! macro we’ve used in the past, we use square
brackets [] with vec! macro. Rust allows you to use either in either situation,
this is just convention.)
There’s an alternate form of vec! for repeating an initial value:
let v = vec![0; 10]; // ten zeroes
Accessing elements
To get the value at a particular index in the vector, we use []s:
let v = vec![1, 2, 3, 4, 5];
println!("The third element of v is {}", v[2]);
The indices count from 0, so the third element is v[2].
Iterating
Once you have a vector, you can iterate through its elements with for. There
are three versions:
let mut v = vec![1, 2, 3, 4, 5];
for i in &v {
println!("A reference to {}", i);
}
for i in &mut v {
println!("A mutable reference to {}", i);
}
for i in v {
println!("Take ownership of the vector and its element {}", i);
}
Vectors have many more useful methods, which you can read about in their API documentation.