macro_rules! vec { () => { ... }; ($elem:expr; $n:expr) => { ... }; ($($x:expr),+ $(,)?) => { ... }; }
Expand description
Creates a Vec
containing the arguments.
vec!
allows Vec
s to be defined with the same syntax as array expressions.
There are two forms of this macro:
- Create a
Vec
containing a given list of elements:
let v = vec![1, 2, 3];
assert_eq!(v[0], 1);
assert_eq!(v[1], 2);
assert_eq!(v[2], 3);
Run- Create a
Vec
from a given element and size:
let v = vec![1; 3];
assert_eq!(v, [1, 1, 1]);
RunNote that unlike array expressions this syntax supports all elements
which implement Clone
and the number of elements doesn’t have to be
a constant.
This will use clone
to duplicate an expression, so one should be careful
using this with types having a nonstandard Clone
implementation. For
example, vec![Rc::new(1); 5]
will create a vector of five references
to the same boxed integer value, not five references pointing to independently
boxed integers.
Also, note that vec![expr; 0]
is allowed, and produces an empty vector.
This will still evaluate expr
, however, and immediately drop the resulting value, so
be mindful of side effects.