I believe that was just showing an example of the error the compiler will
generate when not using trait constraints. If you read a little further, a
similar error is produced from
fn print_area<T>(shape: T) {
println!("This shape has an area of {}", shape.area());
}
Because T can be any type, we can't be sure that it implements the area method.
But we can add a *trait constraint* to our generic T, ensuring that it does:
fn print_area<T: HasArea>(shape: T) {
println!("This shape has an area of {}", shape.area());
}
If you're wanting to do comparisons, you will probably want to place a
trait constraint on your functions from the following module:
http://doc.rust-lang.org/std/cmp/index.html#traits
Nathan Sizemore
@nathansizemore | 937.823.7229
On Fri, Dec 5, 2014 at 6:33 AM, Péter Mózes Merl <[email protected]> wrote:
> Hi Everyone,
>
> after long years of working with scripting languages I have finally found
> a strongly-typed language that is worth to learn (for me). Cheers.
>
> The Guide is awesome. There is only one thing I missed and that’s between
> chapters 22 and 23, Generics and Traits. The Guide says that we have to
> learn about Traits to fix this message:
>
> error: binary operation `==` cannot be applied to type `T`
>
> I think the example how to fix it at the end is missing. I am not sure
> whether this is the right place to provide such a feedback, however, I
> could not find a link in the Guide.
>
> Thank you.
>
> Péter
>
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>
>
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