Merge pull request #3 from sotanengel/main

問題文の追加

Cargo.toml

@@ -14,6 +14,14 @@ bin = [
   { name = "2_function_pointer_sol", path = "solutions/2_types_Use_the_type_system_to_express_common_behavior/2_function_pointer.rs" },
   { name = "3_closure", path = "exercises/2_types_Use_the_type_system_to_express_common_behavior/3_closure.rs" },
   { name = "3_closure_sol", path = "solutions/2_types_Use_the_type_system_to_express_common_behavior/3_closure.rs" },
+  { name = "1_if_let", path = "exercises/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/1_if_let.rs" },
+  { name = "1_if_let_sol", path = "solutions/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/1_if_let.rs" },
+  { name = "2_processing_outsourced", path = "exercises/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/2_processing_outsourced.rs" },
+  { name = "2_processing_outsourced_sol", path = "solutions/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/2_processing_outsourced.rs" },
+  { name = "3_unuse_result_type", path = "exercises/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/3_unuse_result_type.rs" },
+  { name = "3_unuse_result_type_sol", path = "solutions/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/3_unuse_result_type.rs" },
+  { name = "4_sugar_result_process", path = "exercises/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/4_sugar_result_process.rs" },
+  { name = "4_sugar_result_process_sol", path = "solutions/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/4_sugar_result_process.rs" },
 ]
 
 [package]

exercises/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/1_if_let.rs

@@ -0,0 +1,9 @@
+fn main() {
+    let value: Option<i32> = Some(42);
+
+    // TODO: Noneの場合の処理は必要ないのでifを使った処理に変更してください。
+    match value {
+        Some(x) => println!("Found: {}", x),
+        None => println!("No value found."),
+    }
+}

exercises/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/2_processing_outsourced.rs

@@ -0,0 +1,9 @@
+fn main() {
+    let value: Option<i32> = Some(42);
+
+    // TODO: expectを使って冗長な処理を簡潔にしてください。
+    match value {
+        Some(num) => println!("The value is: {}", num),
+        None => panic!("Something wrong !"),
+    };
+}

exercises/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/3_unuse_result_type.rs

@@ -0,0 +1,15 @@
+fn divide(a: i32, b: i32) -> Result<i32, &'static str> {
+    if b == 0 {
+        Err("Division by zero is not allowed")
+    } else {
+        Ok(a / b)
+    }
+}
+
+fn main() {
+    let result = divide(10, 0);
+
+    // TODO: 返却されたResult型は使用する必要があります。
+    // matchを使って、計算結果を表示してください。
+    println!("result is Error");
+}

exercises/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/4_sugar_result_process.rs

@@ -0,0 +1,16 @@
+fn divide(a: i32, b: i32) -> Result<i32, &'static str> {
+    if b == 0 {
+        Err("Division by zero is not allowed")
+    } else {
+        Ok(a / b)
+    }
+}
+
+fn main() {
+    let result = divide(10, 3); // TODO: クエスションマークを使ってさらに簡潔に表現しましょう。
+
+    match result {
+        Ok(value) => println!("Result: {}", value),
+        Err(e) => panic!("Result: {}", e),
+    }
+}

info.toml

@@ -60,3 +60,31 @@ dir = "2_types_Use_the_type_system_to_express_common_behavior"
 test = false
 hint = """クロージャの基本を学びます。環境をキャプチャする関数を理解しましょう。"""
 skip_check_unsolved = false
+
+[[exercises]]
+name = "1_if_let"
+dir = "3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions"
+test = false
+hint = """if let構文を使って、OptionやResultの安全なunwrapを学びます。"""
+skip_check_unsolved = true
+
+[[exercises]]
+name = "2_processing_outsourced"
+dir = "3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions"
+test = false
+hint = """処理を他の関数に委譲する方法を学びます。"""
+skip_check_unsolved = true
+
+[[exercises]]
+name = "3_unuse_result_type"
+dir = "3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions"
+test = false
+hint = """Result型の未使用を防ぐ方法を学びます。"""
+skip_check_unsolved = true
+
+[[exercises]]
+name = "4_sugar_result_process"
+dir = "3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions"
+test = false
+hint = """Result型のシュガー表現を使って、エラーハンドリングを簡潔に記述します。"""
+skip_check_unsolved = true

solutions/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/1_if_let.rs

@@ -0,0 +1,8 @@
+fn main() {
+    let some_value: Option<i32> = Some(42);
+
+    // 値がある場合だけ処理を行う
+    if let Some(x) = some_value {
+        println!("Found: {}", x);
+    }
+}

solutions/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/2_processing_outsourced.rs

@@ -0,0 +1,7 @@
+#[allow(clippy::unnecessary_literal_unwrap)]
+fn main() {
+    let value: Option<i32> = Some(42);
+
+    let result = value.expect("Something wrong !");
+    println!("The value is: {}", result);
+}

solutions/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/3_unuse_result_type.rs

@@ -0,0 +1,16 @@
+fn divide(a: i32, b: i32) -> Result<i32, &'static str> {
+    if b == 0 {
+        Err("Division by zero is not allowed")
+    } else {
+        Ok(a / b)
+    }
+}
+
+fn main() {
+    let result = divide(10, 0);
+
+    match result {
+        Ok(value) => println!("Result: {}", value),
+        Err(e) => println!("Result: {}", e),
+    }
+}

solutions/3_types_Prefer_option_and_result_transforms_over_explicit_match_expressions/4_sugar_result_process.rs

@@ -0,0 +1,14 @@
+fn divide(a: i32, b: i32) -> Result<i32, &'static str> {
+    if b == 0 {
+        Err("Division by zero is not allowed")
+    } else {
+        Ok(a / b)
+    }
+}
+
+fn main() -> Result<(), &'static str> {
+    let value = divide(10, 3)?; // クエスションマークでエラーハンドリング
+    println!("Result: {}", value);
+
+    Ok(())
+}