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56 lines
1.2 KiB
56 lines
1.2 KiB
4 years ago
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## adding_twice
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### Instructions
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In this exercise you will have to reuse your `add_curry` function
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Then you have to complete the function `twice` using closures, this function will
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take a function f(x) as parameter and return a function f(f(x))
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So, the purpose of this function is to add two times the value in `add_curry` to the original value.
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### Notions
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- https://doc.rust-lang.org/rust-by-example/fn/hof.html#higher-order-functions
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### Expected functions
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The type of the arguments are missing use the example `main` function to determine the correct type.
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```rust
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fn twice<T>(F: _) -> _{}
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```
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### Usage
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Here is a program to test your function.
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```rust
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fn main() {
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let add10 = add_curry(10);
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let value = twice(add10);
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println!("The value is {}", value(7));
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let add20 = add_curry(20);
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let value = twice(add20);
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println!("The value is {}", value(7));
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let add30 = add_curry(30);
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let value = twice(add30);
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println!("The value is {}", value(7));
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let neg = add_curry(-32);
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let value = twice(neg);
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println!("The value is {}", value(7));
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}
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```
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And its output
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```console
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student@ubuntu:~/[[ROOT]]/test$ cargo run
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The value is 27
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The value is 47
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The value is 67
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The value is -57
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student@ubuntu:~/[[ROOT]]/test$
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```
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