Rust learning: lessons, notes, and exercise crates

learn-collections/.gitignore

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+/target

learn-collections/Cargo.lock

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

learn-collections/Cargo.toml

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+[package]
+name = "learn-collections"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

learn-collections/src/main.rs

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+enum SpreadsheetCell {
+    Int(i32),
+    Float(f32),
+    Text(String),
+}
+
+fn main() {
+    println!("Hello, world!");
+    let mut v = vec![1, 2, 3, 4];
+
+    v.push(5);
+    v.push(6);
+    v.push(7);
+
+    let Some(&x) = v.get(3) else {
+        println!("index not found");
+        return;
+    };
+
+    for i in &v {
+        print!("{i}");
+    }
+    println!("");
+
+    for i in &mut v {
+        *i = *i * 10;
+    }
+
+    for i in &v {
+        print!("{i}");
+    }
+    println!("");
+
+    println!("this is the value of the 100th index {x}");
+
+    let _row = vec![
+        SpreadsheetCell::Int(3),
+        SpreadsheetCell::Float(3.14),
+        SpreadsheetCell::Text("bodo".into()),
+    ];
+
+    let _s1 = String::from("Hello");
+    let _s2 = "World".to_string();
+    let _s1: String = _s1 + &_s2;
+    println!("THis is: {_s1}");
+    let _s3 = "FooBar".to_string();
+    let _s = format!("{_s1} {_s3}");
+    println!("{}", _s);
+
+    use std::collections::HashMap;
+
+    let mut scores = HashMap::new();
+
+    scores.insert("blue".to_string(), 1);
+    scores.insert("red".to_string(), 3);
+
+    let score_blue = scores.get(&"blue".to_string()).copied().unwrap_or(0);
+    let score_red = scores.get(&"red".to_string()).copied().unwrap_or(0);
+
+    println!("this is blue: {}, this is red {}", score_blue, score_red);
+    for (k, v) in &scores {
+        println!("team {k}: {v} scores");
+    }
+
+    scores.insert("green".to_string(), 10);
+
+    scores.insert(String::from("Blue"), 10);
+    scores.insert(String::from("Blue"), 25);
+
+    println!("{scores:?}");
+
+    scores.entry("blue".to_string()).or_insert(100);
+    scores.entry("yellow".to_string()).or_insert(100);
+
+    println!("{scores:?}");
+}