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Enforce consistent formatting use `dprint`
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Luca Palmieri
2024-05-24 17:00:03 +02:00
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book/src/06_ticket_management/07_combinators.md
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# Combinators
Iterators can do so much more than `for` loops!
If you look at the documentation for the `Iterator` trait, you'll find a **vast** collections of
Iterators can do so much more than `for` loops!\
If you look at the documentation for the `Iterator` trait, you'll find a **vast** collections of
methods that you can leverage to transform, filter, and combine iterators in various ways.
Let's mention the most common ones:
@@ -15,7 +15,7 @@ Let's mention the most common ones:
- `take` stops the iterator after `n` elements.
- `chain` combines two iterators into one.
These methods are called **combinators**.
These methods are called **combinators**.\
They are usually **chained** together to create complex transformations in a concise and readable way:
```rust
@@ -29,10 +29,10 @@ let outcome: u32 = numbers.iter()
## Closures
What's going on with the `filter` and `map` methods above?
What's going on with the `filter` and `map` methods above?\
They take **closures** as arguments.
Closures are **anonymous functions**, i.e. functions that are not defined using the `fn` syntax we are used to.
Closures are **anonymous functions**, i.e. functions that are not defined using the `fn` syntax we are used to.\
They are defined using the `|args| body` syntax, where `args` are the arguments and `body` is the function body.
`body` can be a block of code or a single expression.
For example:
@@ -70,10 +70,10 @@ let add_one: fn(i32) -> i32 = |x| x + 1;
## `collect`
What happens when you're done transforming an iterator using combinators?
What happens when you're done transforming an iterator using combinators?\
You either iterate over the transformed values using a `for` loop, or you collect them into a collection.
The latter is done using the `collect` method.
The latter is done using the `collect` method.\
`collect` consumes the iterator and collects its elements into a collection of your choice.
For example, you can collect the squares of the even numbers into a `Vec`:
@@ -86,7 +86,7 @@ let squares_of_evens: Vec<u32> = numbers.iter()
.collect();
```
`collect` is generic over its **return type**.
`collect` is generic over its **return type**.\
Therefore you usually need to provide a type hint to help the compiler infer the correct type.
In the example above, we annotated the type of `squares_of_evens` to be `Vec<u32>`.
Alternatively, you can use the **turbofish syntax** to specify the type:
@@ -104,4 +104,4 @@ let squares_of_evens = numbers.iter()
- [`Iterator`'s documentation](https://doc.rust-lang.org/std/iter/trait.Iterator.html) gives you an
overview of the methods available for iterators in `std`.
- [The `itertools` crate](https://docs.rs/itertools/) defines even **more** combinators for iterators.
- [The `itertools` crate](https://docs.rs/itertools/) defines even **more** combinators for iterators.