ch13 関数型言語の機能: イテレータとクロージャの和訳を最新版に更新

rust-lang/book@19c40bf

listings/ch13-functional-features/listing-12-23-reproduced/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "minigrep"
 version = "0.1.0"
-authors = ["Your Name <you@example.com>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch13-functional-features/listing-12-23-reproduced/src/lib.rs

@@ -4,42 +4,42 @@ use std::fs;
 
 pub struct Config {
     pub query: String,
-    pub filename: String,
-    pub case_sensitive: bool,
+    pub file_path: String,
+    pub ignore_case: bool,
 }
 
 // ANCHOR: ch13
 impl Config {
-    pub fn new(args: &[String]) -> Result<Config, &'static str> {
+    pub fn build(args: &[String]) -> Result<Config, &'static str> {
         if args.len() < 3 {
             return Err("not enough arguments");
         }
 
         let query = args[1].clone();
-        let filename = args[2].clone();
+        let file_path = args[2].clone();
 
-        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();
+        let ignore_case = env::var("IGNORE_CASE").is_ok();
 
         Ok(Config {
             query,
-            filename,
-            case_sensitive,
+            file_path,
+            ignore_case,
         })
     }
 }
 // ANCHOR_END: ch13
 
 pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
-    let contents = fs::read_to_string(config.filename)?;
+    let contents = fs::read_to_string(config.file_path)?;
 
-    let results = if config.case_sensitive {
-        search(&config.query, &contents)
-    } else {
+    let results = if config.ignore_case {
         search_case_insensitive(&config.query, &contents)
+    } else {
+        search(&config.query, &contents)
     };
 
     for line in results {
-        println!("{}", line);
+        println!("{line}");
     }
 
     Ok(())
@@ -104,5 +104,3 @@ Trust me.";
         );
     }
 }
-
-fn main() {}

listings/ch13-functional-features/listing-12-23-reproduced/src/main.rs

@@ -6,14 +6,13 @@ use minigrep::Config;
 fn main() {
     let args: Vec<String> = env::args().collect();
 
-    let config = Config::new(&args).unwrap_or_else(|err| {
-        println!("Problem parsing arguments: {}", err);
+    let config = Config::build(&args).unwrap_or_else(|err| {
+        println!("Problem parsing arguments: {err}");
         process::exit(1);
     });
 
     if let Err(e) = minigrep::run(config) {
-        println!("Application error: {}", e);
-
+        println!("Application error: {e}");
         process::exit(1);
     }
 }

listings/ch13-functional-features/listing-12-24-reproduced/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "minigrep"
 version = "0.1.0"
-authors = ["Your Name <you@example.com>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch13-functional-features/listing-12-24-reproduced/src/lib.rs

@@ -4,40 +4,40 @@ use std::fs;
 
 pub struct Config {
     pub query: String,
-    pub filename: String,
-    pub case_sensitive: bool,
+    pub file_path: String,
+    pub ignore_case: bool,
 }
 
 impl Config {
-    pub fn new(args: &[String]) -> Result<Config, &'static str> {
+    pub fn build(args: &[String]) -> Result<Config, &'static str> {
         if args.len() < 3 {
             return Err("not enough arguments");
         }
 
         let query = args[1].clone();
-        let filename = args[2].clone();
+        let file_path = args[2].clone();
 
-        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();
+        let ignore_case = env::var("IGNORE_CASE").is_ok();
 
         Ok(Config {
             query,
-            filename,
-            case_sensitive,
+            file_path,
+            ignore_case,
         })
     }
 }
 
 pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
-    let contents = fs::read_to_string(config.filename)?;
+    let contents = fs::read_to_string(config.file_path)?;
 
-    let results = if config.case_sensitive {
-        search(&config.query, &contents)
-    } else {
+    let results = if config.ignore_case {
         search_case_insensitive(&config.query, &contents)
+    } else {
+        search(&config.query, &contents)
     };
 
     for line in results {
-        println!("{}", line);
+        println!("{line}");
     }
 
     Ok(())

listings/ch13-functional-features/listing-12-24-reproduced/src/main.rs

@@ -7,17 +7,16 @@ use minigrep::Config;
 fn main() {
     let args: Vec<String> = env::args().collect();
 
-    let config = Config::new(&args).unwrap_or_else(|err| {
-        eprintln!("Problem parsing arguments: {}", err);
+    let config = Config::build(&args).unwrap_or_else(|err| {
+        eprintln!("Problem parsing arguments: {err}");
         process::exit(1);
     });
 
     // --snip--
     // ANCHOR_END: ch13
 
     if let Err(e) = minigrep::run(config) {
-        eprintln!("Application error: {}", e);
-
+        eprintln!("Application error: {e}");
         process::exit(1);
     }
     // ANCHOR: ch13

listings/ch13-functional-features/listing-13-01/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
-name = "workout-app"
+name = "shirt-company"
 version = "0.1.0"
-authors = ["Your Name <you@example.com>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch13-functional-features/listing-13-01/output.txt

@@ -0,0 +1,6 @@
+$ cargo run
+   Compiling shirt-company v0.1.0 (file:///projects/shirt-company)
+    Finished dev [unoptimized + debuginfo] target(s) in 0.27s
+     Running `target/debug/shirt-company`
+The user with preference Some(Red) gets Red
+The user with preference None gets Blue

listings/ch13-functional-features/listing-13-01/src/main.rs

@@ -1,12 +1,54 @@
-// ANCHOR: here
-use std::thread;
-use std::time::Duration;
+#[derive(Debug, PartialEq, Copy, Clone)]
+enum ShirtColor {
+    Red,
+    Blue,
+}
+
+struct Inventory {
+    shirts: Vec<ShirtColor>,
+}
+
+impl Inventory {
+    fn giveaway(&self, user_preference: Option<ShirtColor>) -> ShirtColor {
+        user_preference.unwrap_or_else(|| self.most_stocked())
+    }
 
-fn simulated_expensive_calculation(intensity: u32) -> u32 {
-    println!("calculating slowly...");
-    thread::sleep(Duration::from_secs(2));
-    intensity
+    fn most_stocked(&self) -> ShirtColor {
+        let mut num_red = 0;
+        let mut num_blue = 0;
+
+        for color in &self.shirts {
+            match color {
+                ShirtColor::Red => num_red += 1,
+                ShirtColor::Blue => num_blue += 1,
+            }
+        }
+        if num_red > num_blue {
+            ShirtColor::Red
+        } else {
+            ShirtColor::Blue
+        }
+    }
 }
-// ANCHOR_END: here
 
-fn main() {}
+fn main() {
+    let store = Inventory {
+        shirts: vec![ShirtColor::Blue, ShirtColor::Red, ShirtColor::Blue],
+    };
+
+    let user_pref1 = Some(ShirtColor::Red);
+    let giveaway1 = store.giveaway(user_pref1);
+    println!(
+        // "好み{:?}を持つユーザは{:?}を得ます"
+        "The user with preference {:?} gets {:?}",
+        user_pref1, giveaway1
+    );
+
+    let user_pref2 = None;
+    let giveaway2 = store.giveaway(user_pref2);
+    println!(
+        // "好み{:?}を持つユーザは{:?}を得ます"
+        "The user with preference {:?} gets {:?}",
+        user_pref2, giveaway2
+    );
+}

listings/ch13-functional-features/listing-13-02/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
 name = "workout-app"
 version = "0.1.0"
-authors = ["Your Name <you@example.com>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch13-functional-features/listing-13-02/src/main.rs

@@ -1,19 +1,33 @@
 use std::thread;
 use std::time::Duration;
 
-fn simulated_expensive_calculation(intensity: u32) -> u32 {
-    println!("calculating slowly...");
-    thread::sleep(Duration::from_secs(2));
-    intensity
-}
+fn generate_workout(intensity: u32, random_number: u32) {
+    // ANCHOR: here
+    let expensive_closure = |num: u32| -> u32 {
+        println!("calculating slowly...");
+        thread::sleep(Duration::from_secs(2));
+        num
+    };
+    // ANCHOR_END: here
 
-fn generate_workout(intensity: u32, random_number: u32) {}
+    if intensity < 25 {
+        println!("Today, do {} pushups!", expensive_closure(intensity));
+        println!("Next, do {} situps!", expensive_closure(intensity));
+    } else {
+        if random_number == 3 {
+            println!("Take a break today! Remember to stay hydrated!");
+        } else {
+            println!(
+                "Today, run for {} minutes!",
+                expensive_closure(intensity)
+            );
+        }
+    }
+}
 
-// ANCHOR: here
 fn main() {
     let simulated_user_specified_value = 10;
     let simulated_random_number = 7;
 
     generate_workout(simulated_user_specified_value, simulated_random_number);
 }
-// ANCHOR_END: here

listings/ch13-functional-features/listing-13-03/Cargo.toml

@@ -1,7 +1,6 @@
 [package]
-name = "workout-app"
+name = "closure-example"
 version = "0.1.0"
-authors = ["Your Name <you@example.com>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]

listings/ch13-functional-features/listing-13-03/output.txt

@@ -0,0 +1,33 @@
+$ cargo run
+   Compiling closure-example v0.1.0 (file:///projects/closure-example)
+error[E0308]: mismatched types
+(エラー: 型が合いません)
+ --> src/main.rs:5:29
+  |
+5 |     let n = example_closure(5);
+  |             --------------- ^- help: try using a conversion method: `.to_string()`
+  |             |               | (ヘルプ: 変換メソッド`.to_string()`を使用してみてください)
+  |             |               |
+  |             |               expected `String`, found integer
+  |             |              (`String`を予期していましたが、整数が見つかりました)
+  |             arguments to this function are incorrect
+  |            (この関数への引数が正しくありません)
+  |
+note: expected because the closure was earlier called with an argument of type `String`
+(注釈: クロージャは以前に型`String`を持つ引数とともに呼ばれているため、これが予期されています)
+ --> src/main.rs:4:29
+  |
+4 |     let s = example_closure(String::from("hello"));
+  |             --------------- ^^^^^^^^^^^^^^^^^^^^^ expected because this argument is of type `String`
+  |             |                                    (この引数が型`String`を持つことから予期されています)
+  |             |
+  |             in this closure call
+  |            (このクロージャ呼び出しで)
+note: closure parameter defined here
+ --> src/main.rs:2:28
+  |
+2 |     let example_closure = |x| x;
+  |                            ^
+
+For more information about this error, try `rustc --explain E0308`.
+error: could not compile `closure-example` (bin "closure-example") due to 1 previous error