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Feature suggestion: impl Default for Zip, and add Zip::with_shape() constructor

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評估

難度
5/5
預估耗時
一週以上
新手友好度
35/100
Issue 類型
功能
描述清晰度
基本清楚
活躍度
停滯
技術堆疊
rust
領域
data

研究方向

Start by reviewing the existing Zip::from, Zip::and, and and_broadcast entry points and how they handle shapes and broadcasting. Compare the proposed Default and Zip::with_shape APIs with the motivating example; done means the API direction and resulting behavior are clearly agreed and validated.

由索引模型根據 Issue 內容生成。

描述

Motivating example: I'm computing 3D positions on a unit sphere from a uniform grid of (longitude, latitude) pairs. This is what it looks like now:

        const SHAPE: (usize, usize) = (HEIGHT, WIDTH);
        let cell_size_lon = TAU / WIDTH as f32;
        let cell_size_lat = PI / HEIGHT as f32;
        let lon = Array1::linspace(cell_size_lon, TAU - cell_size_lon, WIDTH)
            .into_shape((1, WIDTH)).unwrap();
        let lat = Array1::linspace(-FRAC_PI_2 + cell_size_lat, FRAC_PI_2 - cell_size_lat, HEIGHT)
            .into_shape((HEIGHT, 1)).unwrap();
        let pos = Zip::from(lat.mapv(f32::cos).broadcast(SHAPE).unwrap())
            .and(lat.mapv(f32::sin).broadcast(SHAPE).unwrap())
            .and(lon.mapv(f32::cos).broadcast(SHAPE).unwrap())
            .and(lon.mapv(f32::sin).broadcast(SHAPE).unwrap())
            .par_map_collect(|&cos_lat, &sin_lat, &cos_lon, &sin_lon| {
                Vec3::new(cos_lat * sin_lon, sin_lat, cos_lat * cos_lon)
            });

I know about azip! and par_azip! but I don't think the small reduction in character count outweighs the additional "magic" syntax, so I don't use them.

Notice the distinction between Zip::from and Zip::and even though these both serve the same purpose: add another producer to the Zip.

This lopsided distinction could be eliminated if Zip implemented Default (and/or had the customary zero-args new() constructor):

        let pos = Zip::default()
            .and(lat.mapv(f32::cos).broadcast(SHAPE).unwrap())
            .and(lat.mapv(f32::sin).broadcast(SHAPE).unwrap())
            .and(lon.mapv(f32::cos).broadcast(SHAPE).unwrap())
            .and(lon.mapv(f32::sin).broadcast(SHAPE).unwrap())
            .par_map_collect(|&cos_lat, &sin_lat, &cos_lon, &sin_lon| {
                Vec3::new(cos_lat * sin_lon, sin_lat, cos_lat * cos_lon)
            });

Even nicer (for this use case) would be if we could specify the shape once up front in the constructor, so we could use and_broadcast on all producers (not just the 2nd-4th):

        let pos = Zip::with_shape(SHAPE)
            .and_broadcast(lat.mapv(f32::cos))
            .and_broadcast(lat.mapv(f32::sin))
            .and_broadcast(lon.mapv(f32::cos))
            .and_broadcast(lon.mapv(f32::sin))
            .par_map_collect(|&cos_lat, &sin_lat, &cos_lon, &sin_lon| {
                Vec3::new(cos_lat * sin_lon, sin_lat, cos_lat * cos_lon)
            });

I can't tell whether this is at all feasible or desirable, just throwing it out there for your consideration, and so that other users with similar needs can chime in.

主要語言
Rust
星號
4.3k
分支
391
30 天內沒有已合併 PR

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  3. Fork 儲存庫，在一個分支上完成修改。
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