Generic over integers, convertable to string

Say I have a HashMap<String, String> and I want to be able to add parameters, of different types, to it. Here's a string example:

struct MyFoo {
  params: HashSet<String, String>

impl MyFoo {
  fn add_string<T: AsRef<str>, U: AsRef<str>>(&mut self, key: T, value: U) {
    // ...

Now I would like to add an add_int method that is generic over any integer type. I.e. it should accept obj.add_int("foo", 3 as i16) as well as obj.add_int("bar", 5 as usize), convert the input to a string and add them to the HashMap. I saw some other - years old - posts that hint that there was an RFC which would allow this. Is there a way to accomplish this using a single generic method?

You could use the Integer trait from the num-integer crate and also Display:

fn add_int<T: AsRef<str>, U: Integer + Display>(&mut self, key: T, value: U) {
    let value = value.to_string();

Is there a reason you want to limit it to integers and not just all types that implement Display (or really ToString?)

1 Like

I guess not. There's already an add_param() that uses ToString. The more specific functions are there for API look'n'feel parity with an existing C++ library. We want C++ developers who want to try to use Rust for client applications to feel right at home with the interfaces.

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