Write a function called `doubtful` that adds to every string passed to it a question mark (?).
You have to complete the signature the functions to make it fit the usage and you also have to modify the usage to be able to do what is expected.
- Restrictions:
- `doubtful` cannot return any value.
- And in the example of the usage you can only modify the argument of the function
### Expected
Create a function named `doubtful` which appends a question mark to every string passed to it. It must not return a value.
```rust
pub fn doubtful(s: /*give the correct type*/ ) {
}
```
You'll need to complete the function signature, so that it works properly with the usage example. You'll also need to complete the usage if you plan to use it.
davhojt
2 years ago
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