# Objective
This was always a bit weird; `IntoIterator` is considered more idiomatic
in Rust.
The reason these used `Into<Vec<..>>` in the first place was (to my
knowledge) because of concerns that passing an already-owned vector
would cause a redundant allocation if the iterator API was used instead.
However, I have looked at simple examples for this scenario and the
generated assembly is identical (i.e. `into_iter().collect()` is
effectively converted to a no-op).
## Solution
As described in the title.
## Testing
It compiles. Ran existing tests.
## Migration Guide
The cubic splines API now uses `IntoIterator` in places where it used
`Into<Vec<..>>`. For most users, this will have little to no effect (it
is largely more permissive). However, in case you were using some
unusual input type that implements `Into<Vec<..>>` without implementing
`IntoIterator`, you can migrate by converting the input to a `Vec<..>`
before passing it into the interface.
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