Tuples in Rust
Learn how to represent multiple values of different type using a single type by leveraging the power of tuples in Rust.
Course
Basic Types in Rust
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Instructor: Tuples are collections of values that can have different types. To create a tuple, we write a sequence of values separated by commas, surrounded by parentheses.
For example, we could create a variable point that represents a point in a coordinate system using a tuple like this. In this case, the tuple would be of type (i32, i32). However, it's totally possible for a tuple to have different types.
Tuples can have more than two values as well. For example, we could say a point has an id, which in this case would be of type string. Then the tuple would become a triple of type (string, i32, i32).
To access the values of a tuple, we would use constant indexes. In this case, we could say println!. Then we say Point placeholder, then placeholder, another_placeholder. Then we give it point.0and point.1 and point.2. When we save and run this program, we'll see it'll output Point A, 32, 34.
Tuples are useful for cases where we want to represent multiple values of different type as a single type without necessarily introducing a new custom type. Just like any other type in Rust, a tuple can be returned from functions as well.
For example, if we have a text of "Hello, world," we could call its split method on it, which would return a head and tail of the text. In this case, the returned value would be a tuple of type string slice reference and string slice reference.
Tuples can hold up to 12 values. For consistency's sake, a tuple can hold a single value as well. We could have a variable a of type tuple, some_value. This would be totally valid. Notice, however, that there is a trailing comma here. This is needed in order to have Rust distinguish between this tuple expression from a simple expression such as 1 + 1.
Another interesting type. This seems functionally similar to any[] in TypeScript, only with a maximum length. Is tuple the only option in Rust for an array-like of mixed types? Short of creating your own custom types, I mean.
Tuples can hold up to 12 values.
I'm confused about this. I tried creating a tuple bigger than that just to see what would happen:
let tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14);
println!("14th value: {}", tuple.13);It still works.
let (head, tail) = text.split_at(5);
I appreciate that Rust allows this kind of destructuring syntax, as opposed to requiring something like this:
let split = text.split_at(5);
let head = split.0;
let tail = split.1;
This seems functionally similar to any[] in TypeScript, only with a maximum length.
Not exactly, because any[] doesn't dictate the order of types in use while a tuple (e.g. (i32, &str, String)) does.
Is tuple the only option in Rust for an array-like of mixed types?
I think so. There are other collection types like HashMap<K, V>, where K and V can be of different type, this of course also has different semantics.
I'm confused about this. I tried creating a tuple bigger than that just to see what would happen:
To be honest, I trusted the number I've read in my book and never verified it myself. Very good catch! Will update this episode accordingly!!
Say I update part of a tuple with new values. Must the type order remain the same?
Hey Anthony,
yes, the order has to remain the same otherwise you'd actually change the type of value. So for example:
let mut point = ("A", 8, 9); // (&str, i32, i32) <- this is the current type
point.0 = "B"; // <- this works fine as `point` is mutable and `point.0` is of type `&str`
point.0 = 3; // <- this will be a compilation error because the expected type of `point.0` is `&str` (per initialization)Makes sense! Thanks, Pascal!
Great courses so far! They are to the point and pack a lot of information. I appreciate your style.
I have learnt a lot!