chart context as parameter

[PicoJr]

Hello, how would you extract the following code into its own function?

    chart
        .draw_series(LineSeries::new(
            (-100..100)
                .map(|y| y as f64 / 40.0)
                .map(|y| ((y * 10.0).sin(), y, (y * 10.0).cos())),
            &BLACK,
        ))?
        .label("Line")
        .legend(|(x, y)| PathElement::new(vec![(x, y), (x + 20, y)], &BLACK));

What I tried:

fn my_function<DB, CT>(
    chart: &mut ChartContext<DB, CT>,
) -> Result<(), Box<dyn std::error::Error>>
where
    DB: DrawingBackend,
    CT: CoordTranslate,
{
    chart
        .draw_series(LineSeries::new(
            (-100..100)
                .map(|y| y as f64 / 40.0)
                .map(|y| ((y * 10.0).sin(), y, (y * 10.0).cos())),
            &BLACK,
        ))?
        .label("Line")
        .legend(|(x, y)| PathElement::new(vec![(x, y), (x + 20, y)], &BLACK));
    Ok(())
}

The compiler complains:

   |
28 |         .draw_series(LineSeries::new(
   |          ^^^^^^^^^^^ the trait `for<'b> PointCollection<'b, <CT as plotters::coord::CoordTranslate>::From>` is not implemented for `&'b DynElement<'static, DB, (f64, f64, f64)>`
   |
help: consider extending the `where` bound, but there might be an alternative better way to express this requirement
   |
25 |     CT: CoordTranslate, &'b DynElement<'static, DB, (f64, f64, f64)>: for<'b> PointCollection<'b, <CT as plotters::coord::CoordTranslate>::From>
   |                       

I also tried constraining types more since the apparent type of chart in my case is ChartContext<SVGBackend, Cartesian3D<Linspace<RangedCoordf64, f64, Exact<f64>, Linspace<RangedCoordf64, f64, Exact<f64>, Linspace<RangedCoordf64, f64, Exact<f64>>

The issue is that Exact<f64> is not public?

Thanks for your help,

[SallySoul]

I want to bump this issue, I haven't found a solution myself, and the result is either code duplication or unattractive workarounds.

I'm happy to help or work on a PR if the y'all have any pointers or thoughts on how you would like this handled.

[facorread]

Hi, I would like to look into the issue; would you be so kind as to provide a Complete example?

On first sight, I would suggest creating a closure instead of a function.

[AlanRace]

I am also having this issue - so here is a complete example:

use plotters::{prelude::*, series::LineSeries};

fn x_squared<'a, DB: DrawingBackend, CT: CoordTranslate>(chart: &mut ChartContext<'a, DB, CT>) {
    chart
        .draw_series(LineSeries::new(
            (-100..100).map(|int_value| {
                let x = int_value as f64 / 10.0;

                (x, x.powf(2.0))
            }),
            &RED,
        ))
        .unwrap();
}

fn main() {
    let root = BitMapBackend::new("0.png", (640, 480)).into_drawing_area();
    root.fill(&WHITE).unwrap();

    let mut chart = ChartBuilder::on(&root)
        //.caption("y=x^2", ("sans-serif", 50).into_font())
        .margin(5)
        .x_label_area_size(50)
        .y_label_area_size(80)
        .build_cartesian_2d(-10.0..10.0, 0.0..100.0)
        .unwrap();

    chart.configure_mesh().draw().unwrap();

    x_squared(&mut chart);

    root.present().unwrap();
}

This results in the error:

error[E0277]: the trait bound `for<'b> &'b DynElement<'static, DB, (f64, f64)>: PointCollection<'b, <CT as plotters::coord::CoordTranslate>::From>` is not satisfied
   --> src/main.rs:6:10
    |
6   |         .draw_series(LineSeries::new(
    |          ^^^^^^^^^^^ the trait `for<'b> PointCollection<'b, <CT as plotters::coord::CoordTranslate>::From>` is not implemented for `&'b DynElement<'static, DB, (f64, f64)>`

[AlanRace]

Changing the function signature to:

fn x_squared<DB: DrawingBackend, CT: CoordTranslate<From = (f64, f64)>>(
    chart: &mut ChartContext<DB, CT>,
) {
...
}

Worked for me.