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## ownership
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### Instruction
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- Create a **function** that takes ownership of a string and returns the first sub-word in it
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- It should work for `camelCase` as well as `snake_case`
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### Notions
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- [ownership](https://doc.rust-lang.org/book/ch04-00-understanding-ownership.html)
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### Expected Function
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```rust
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pub fn first_subword(mut s: String) -> String {
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}
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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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use ownership::first_subword;
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fn main() {
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let s1 = String::from("helloWorld");
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let s2 = String::from("snake_case");
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let s3 = String::from("CamelCase");
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let s4 = String::from("just");
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println!("first_subword({}) = {}", s1.clone(), first_subword(s1));
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println!("first_subword({}) = {}", s2.clone(), first_subword(s2));
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println!("first_subword({}) = {}", s3.clone(), first_subword(s3));
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println!("first_subword({}) = {}", s4.clone(), first_subword(s4));
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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:~/ownership/test$ cargo run
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first_subword(helloWorld) = hello
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first_subword(snake_case) = snake
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first_subword(CamelCase) = Camel
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first_subword(just) = just
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student@ubuntu:~/ownership/test$
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```
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