How to properly concatenate strings in Rust: concat, format! or something else?

Hello everyone! I just started learning Rust, and I encountered a seemingly simple problem — string concatenation. In other languages (Python, JavaScript) I just wrote `"a" + "b"` and it worked. But in Rust the `+` operator behaves strangely. Here's my code: ```rust let hello = "Hello"; let world = "World"; let message = hello + " " + world; // Error! ``` The compiler gives an error: `cannot add `&str` to `&str``. I read that I need to use `to_string()`, but then the code becomes cumbersome: ```rust let message = hello.to_string() + " " + world; // Works, but ugly ``` What if I have many strings, for example, a list of names? Or need to insert a number? I tried `format!`, but heard it's slow. Tell me, how is string concatenation done in Rust? What are the ways and which one is