Comparing string in Rust

rust

Solution

First of all, the line contains the line terminator. You probably want to use `trim` (or one of its variants) to ignore that.

Secondly, you're doing a lot of unnecessary conversions and allocations. Try to avoid those.

Third, `to_string` is (or at least, was the last time I checked) inefficient due to over-allocation. You want `into_string`.

Fourth, the quickest way to go from a `String` to a `&str` is to "cross-borrow" it; given a `String` `s`, `&*s` will re-borrow it as a `&str`. This is because a `String` implements `Deref<&str>`; in other words, `String` acts kind of like a smart pointer to a borrowed string, allowing it to decay into a simpler form.

Fifth, unless you're doing something unusual, you can rewrite this as a `for` loop using the `lines` iterator method.

Sixth, be aware that `stdin()` actually allocates a new buffered reader every time you call it. Not only that, but characters read into the buffer do not get "pushed back" into STDIN when a new buffer is created; that data is simply lost. So you really don't want to be calling it in a loop. If you need to, call it once and keep the result in a variable.

So, I end up with this:

fn main() {
    for line in std::io::stdin().lines() {
        // Extract the line, or handle the error.
        let line = match line {
            Ok(line) => line,
            Err(err) => panic!("failed to read line: {}", err)
        };

        assert_eq!(line.trim(), "exit");
    }
}

Problem

I want to compare a string input from stdin to a static string with no luck. Here is what I have tried so far: ``` fn main() -> () { let mut line = "".to_string(); let exit = "exit".to_string(); while line.as_slice() != exit.as_slice() { let input = std::io::stdin().read_line().ok(); line.push_str( input.unwrap().to_string().as_slice() ); assert_eq!(line, exit); } } ``` However during assertion it failed. How should I compare a string input to a static string in Rust? Your help is very much appreciated.

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