add DataPointLike trait

[0x8f701]

Signed-off-by: Cheng JIANG [email protected]

Hi I added DataPointLike trait, I'd like to remove Copy bound but have no idea on how to do it.

[jeromefroe]

Hi @GopherJ! Thanks for the PR! Code changes look good to me, I'm just curious what the motivation for the PR is, is it so users can implement the DataPointLike trait for their own types and call the lttb function with it? That seems like it would be a great improvement to me.

On a side note, what do you think of renaming DataPointLike to Coordinates? The latter just seems cleaner to me but I'm curious what you think?

Off the top of my head, I think if we want to remove the Copy bound we'll need to change the lttb function to consume the input vector. Currently, we just copy values from the input vector into the output vector (e.g. sampled.push(data[a]);). If, on the other hand, we used a for loop to consume the input vector as we iterate over it we wouldn't need the Copy bound because the input vector will no longer be accessible. Something like the following perhaps:

for (i, v) in data.into_iter().enumerate() {
    if i == 0 {
        // Always add the first point.
        sampled.push(v);
    }

    // ...
}