〇 assert_eq!(m1.get("b"), Some(&3)); ✕ assert_eq!(m1.get("b"), Some(3)); ✕ assert_eq!(m1.get("b"), &3); ✕ assert_eq!(m1.get("b"), 3); 〇 assert_eq!(m1.get("c"), None); PS > cargo run --example ch05_04_hash_map Compiling ex05 v0.1.0 (\rust…

fn main() { let n1 = 10_000; let n2 = 0u8; let n3 = -100_isize; let n4 = 10; let n5 = n3 + n4; } help: consider prefixing with an underscore: _n1 のワーニングがでる。 PS > cargo run --example "ch04_03_integer" warning: file found to be pre…