This block describes the typing incorrectly. #42
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Consider the following demonstration (this code compiles under Rust 2018
as a drop in for the contents of main.rs after `cargo new mapdemo --bin;
cargo run`):
```
fn main() {
let x = [1, 2, 3, 4, 5];
let z = x.iter().map(|&x| format!("{}", x)).collect::<Vec<String>>();
println!("{:?}", z);
}
```
The `self` argument to map will be an `Iter<u64>`. The `Self::Item`
type is therefore `u64`. The return type of the function being passed
to map is `String`. This is what the `B` type variable indicates: the
return type of the function, as can be clearly seen in the second line
of the `where` clause in your example:
```
F: FnMut(Self::Item) -> B
```
|
Thank you! I also see that http://hemingwayapp.com/ is happy with the way you phrased it. |
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Consider the following demonstration (this code compiles under Rust 2018 as a drop in for the contents of main.rs after
cargo new mapdemo --bin, editmain.rs, and thencargo run):This prints an array of strings:
The
selfargument to map will be anIter<u64>. TheSelf::Itemtype is thereforeu64. The return type of the function being passed to map isString. This is what theBtype variable indicates: the return type of the function, as can be clearly seen in the second line of thewhereclause in your example: