Data commit

Task/Goldbachs-comet/Rust/goldbachs-comet.rust

@@ -0,0 +1,75 @@
+// [dependencies]
+// primal = "0.3"
+// plotters = "0.3.2"
+
+use plotters::prelude::*;
+
+fn goldbach(n: u64) -> u64 {
+    let mut p = 2;
+    let mut count = 0;
+    loop {
+        let q = n - p;
+        if q < p {
+            break;
+        }
+        if primal::is_prime(p) && primal::is_prime(q) {
+            count += 1;
+        }
+        if p == 2 {
+            p += 1;
+        } else {
+            p += 2;
+        }
+    }
+    count
+}
+
+fn goldbach_plot(filename: &str) -> Result<(), Box<dyn std::error::Error>> {
+    let gvalues : Vec<u64> = (1..=2000).map(|x| goldbach(2 * x + 2)).collect();
+    let mut gmax = *gvalues.iter().max().unwrap();
+    gmax = 10 * ((gmax + 9) / 10);
+
+    let root = SVGBackend::new(filename, (1000, 500)).into_drawing_area();
+    root.fill(&WHITE)?;
+
+    let mut chart = ChartBuilder::on(&root)
+        .x_label_area_size(20)
+        .y_label_area_size(20)
+        .margin(10)
+        .caption("Goldbach's Comet", ("sans-serif", 24).into_font())
+        .build_cartesian_2d(0usize..2000usize, 0u64..gmax)?;
+
+    chart
+        .configure_mesh()
+        .disable_x_mesh()
+        .disable_y_mesh()
+        .draw()?;
+
+    chart.draw_series(
+        gvalues
+            .iter()
+            .cloned()
+            .enumerate()
+            .map(|p| Circle::new(p, 2, BLUE.filled())),
+    )?;
+
+    Ok(())
+}
+
+fn main() {
+    println!("First 100 G numbers:");
+    for i in 1..=100 {
+        print!(
+            "{:2}{}",
+            goldbach(2 * i + 2),
+            if i % 10 == 0 { "\n" } else { " " }
+        );
+    }
+
+    println!("\nG(1000000) = {}", goldbach(1000000));
+
+    match goldbach_plot("goldbach.svg") {
+        Ok(()) => {}
+        Err(error) => eprintln!("Error: {}", error),
+    }
+}