Rust learning: lessons, notes, and exercise crates

grader/.gitignore

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+/target

grader/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "grader"
+version = "0.1.0"

grader/Cargo.toml

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+[package]
+name = "grader"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

grader/src/main.rs

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+use std::env;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() < 2 {
+        println!("usage : cargo run -- [score]");
+        return;
+    }
+
+    let mut scores: Vec<u32> = Vec::new();
+    for arg in &args[1..] {
+        match arg.parse::<u32>() {
+            Ok(score) => {
+                println!("{score} -> {}", grade_score(score));
+                scores.push(score);
+            }
+            Err(_) => println!("{arg} not a number"),
+        }
+    }
+
+    if scores.is_empty() {
+        println!("not a valid score");
+    } else {
+        println!("average scores: {}", average(&scores));
+    }
+
+    println!("{args:?}");
+}
+
+fn grade_score(score: u32) -> String {
+    match score {
+        90..=100 => "A".to_string(),
+        80..90 => "B".to_string(),
+        70..80 => "C".to_string(),
+        _ => "F".to_string(),
+    }
+}
+
+fn average(scores: &Vec<u32>) -> u32 {
+    let mut total = 0;
+    for s in scores {
+        total = total + s;
+    }
+
+    total / scores.len() as u32
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn grade_map_to_letters() {
+        assert_eq!(grade_score(95), "A");
+        assert_eq!(grade_score(70), "B");
+        assert_eq!(grade_score(43), "F");
+    }
+
+    #[test]
+    fn average_of_three() {
+        assert_eq!(average(&vec![80, 90, 70]), 80);
+    }
+}