Summary - Generics
- Rust course
- Intermediate
- Lesson 12/115
- 5 min
Combine generic struct, method and enum to build Pair<T>.
Generics summary
Generics let you write type-independent code: functions (fn f<T>), structs (struct S<T>), enums (enum E<T>) and methods (impl<T> S<T>). Trait bounds say what can be done with T. A concrete-type impl S<f64> can be written. When the type can't be inferred, the turbofish ::<T> is used. Thanks to monomorphization there's no runtime cost.
A swap function
Some generics need no trait bound at all: a function that only moves values doesn't need to know anything about T:
fn takas<T>(c: (T, T)) -> (T, T) {
(c.1, c.0)
}
println!("{:?}", takas((1, 2))); // (2, 1)But since printing with {:?} happens on the caller's side, T: Debug is needed there, not in the function itself.
Practice Swap
Write the function fn takas<T>(c: (T, T)) -> (T, T) above. Print the results of takas((1, 2)) and takas(("a", "b")) with {:?}, separated by a space.
Starter code
fn main() {
// buraya yaz
}Sample solution
fn takas<T>(c: (T, T)) -> (T, T) {
(c.1, c.0)
}
fn main() {
println!("{:?} {:?}", takas((1, 2)), takas(("a", "b")));
}Expected output
(2, 1) ("b", "a")
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 If a generic function is called with 3 different types, how many copies does the compiler produce?
- 3 Correct answer
- 1
- It's decided at runtime
- 0
Explanation: Monomorphization produces a separate, optimized version for each concrete type.
2 Unbounded generic
fn takas____(c: (T, T)) -> (T, T) {
(c.1, c.0)
}fn takas<T>(c: (T, T)) -> (T, T) {
(c.1, c.0)
}Explanation: A function that only moves values needs no bound.
3 Group summary
| Term | Meaning |
|---|---|
fn f<T>(x: T) |
Generic function |
struct S<T> |
Generic struct |
impl<T> S<T> |
Generic methods |
::<T> |
Turbofish |