arrow2::io::ipc::read::reader::FileReader cannot set 0 as projection

[illumination-k]

Hi, Thanks for the very excellent project!

I would like to parse IPC files, but I cannot set 0 as projection like arrow2::io::ipc::read::reader::FileReader::new(&mut reader, metadata, vec![0, 1]). The cause of this seems to come from

arrow2/src/io/ipc/read/reader.rs

Lines 237 to 243 in add3e2a

	pub fn new(reader: R, metadata: FileMetadata, projection: Option<Vec<usize>>) -> Self {
	if let Some(projection) = projection.as_ref() {
	let _ = projection.iter().fold(0, |mut acc, v| {
	assert!(
	*v > acc,
	"The projection on IPC must be ordered and non-overlapping"
	);

If projection is vec![0, 1], both acc and v equal 0, so error occurred.

It seems that code like this is correct,

let _ = projection.iter().fold(0, |mut acc, v| {
    if !(acc == 0 && *v == 0) {
        assert!( 
            *v > acc, 
            "The projection on IPC must be ordered and non-overlapping" 
        ); 
    }
    acc = *v;
    acc
});

Can I create the PR?

[jorgecarleitao]

Hey! Thanks for the report. Sure, shoot it and I will give it a review :)

[Dandandan]

What about changing the initial acc to -1 ;)?

Even better / idiomatic would be to use windows(2) over the slice.

[illumination-k]

Thanks for your kind comments. I open the pr according to the comments!