乱数のサンプルコード : より説明的なコードにするために乱数のシードを一旦変数にもつようにした

Author: faithandbrave

GLOBAL_QUALIFY_LIST.txt

@@ -251,7 +251,6 @@
     * std::mt19937[link /reference/random/mt19937.md]
     * std::random_device[link /reference/random/random_device.md]
     * std::uniform_int_distribution[link /reference/random/uniform_int_distribution.md]
-    * seed_gen()[link /reference/random/random_device/op_call.md]
 * <ranges>[link /reference/ranges.md]
     * std::ranges::owning_view[link /reference/ranges/owning_view.md]
     * std::ranges::ref_view[link /reference/ranges/ref_view.md]

lang/cpp11/thread_local_storage.md

@@ -51,13 +51,15 @@ t2.join();
 #include <iostream>
 #include <thread>
 #include <random>
+#include <cstdint>
 
 // 範囲[min_inclusive, max_inclusive]でランダム一様分布する整数を生成する。
 // スレッドごとに乱数の状態を持つ。
 int random_range(int min_inclusive, int max_inclusive)
 {
   std::random_device seed_gen;
-  thread_local std::mt19937 engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  thread_local std::mt19937 engine(seed);
   std::uniform_int_distribution<int> dist(min_inclusive, max_inclusive);
   return dist(engine);
 }

reference/algorithm/ranges_shuffle.md

@@ -58,6 +58,7 @@ namespace std::ranges {
 #include <numeric>
 #include <iterator>
 #include <random>
+#include <cstdint>
 
 int main() {
   std::vector<int> v(10);
@@ -69,7 +70,8 @@ int main() {
 
   // シャッフル
   std::random_device seed_gen;
-  std::mt19937 engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::mt19937 engine(seed);
   std::ranges::shuffle(v, engine);
 
   std::cout << " after: ";
@@ -92,6 +94,7 @@ before: 0123456789
 #include <iostream>
 #include <string>
 #include <random>
+#include <cstdint>
 
 int main() {
   std::string input = "0123456789abcdef";
@@ -100,7 +103,8 @@ int main() {
 
   // シャッフル
   std::random_device seed_gen;
-  std::mt19937 engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::mt19937 engine(seed);
   std::ranges::shuffle(input, engine);
 
   std::cout << " after: " << input << std::endl;

reference/algorithm/shuffle.md

@@ -43,6 +43,7 @@ namespace std {
 #include <numeric>
 #include <iterator>
 #include <random>
+#include <cstdint>
 
 int main() {
   std::vector<int> v(10);
@@ -54,7 +55,8 @@ int main() {
 
   // シャッフル
   std::random_device seed_gen;
-  std::mt19937 engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::mt19937 engine(seed);
   std::shuffle(v.begin(), v.end(), engine);
 
   std::cout << " after: ";
@@ -76,6 +78,7 @@ before: 0123456789
 #include <iostream>
 #include <string>
 #include <random>
+#include <cstdint>
 
 int main() {
   std::string input = "0123456789abcdef";
@@ -84,7 +87,8 @@ int main() {
 
   // シャッフル
   std::random_device seed_gen;
-  std::mt19937 engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::mt19937 engine(seed);
   std::shuffle(input.begin(), input.end(), engine);
 
   std::cout << " after: " << input << std::endl;

reference/random.md

@@ -155,13 +155,15 @@
 ```cpp example
 #include <fstream>
 #include <random>
+#include <cstdint>
 
 int main()
 {
   // メルセンヌ・ツイスター法による擬似乱数生成器を、
   // ハードウェア乱数をシードにして初期化
   std::random_device seed_gen;
-  std::mt19937 engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::mt19937 engine(seed);
 
   // 一様実数分布
   // [-1.0f, 1.0f)の値の範囲で、等確率に実数を生成する

reference/random/bernoulli_distribution.md

@@ -72,11 +72,13 @@ namespace std {
 ```cpp example
 #include <random>
 #include <fstream>
+#include <cstdint>
 
 int main()
 {
   std::random_device seed_gen;
-  std::default_random_engine engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::default_random_engine engine(seed);
 
   // 確率0.7でtrueを生成し、確率0.3(1.0 - 0.7)でfalseを生成する
   std::bernoulli_distribution dist(0.7);

reference/random/bernoulli_distribution/op_call.md

@@ -31,11 +31,13 @@ result_type operator()(URBG& g, const param_type& parm); // (2)
 ```cpp example
 #include <iostream>
 #include <random>
+#include <cstdint>
 
 int main()
 {
   std::random_device seed_gen;
-  std::mt19937 engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::mt19937 engine(seed);
 
   std::cout << std::boolalpha;
 

reference/random/bernoulli_distribution/op_constructor.md

@@ -31,11 +31,13 @@ explicit bernoulli_distribution(const param_type& parm);  // (3)
 ```cpp example
 #include <iostream>
 #include <random>
+#include <cstdint>
 
 int main()
 {
   std::random_device seed_gen;
-  std::default_random_engine engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::default_random_engine engine(seed);
 
   std::cout << std::boolalpha;
 

reference/random/bernoulli_distribution/reset.md

@@ -30,11 +30,13 @@ void reset();
 ```cpp example
 #include <iostream>
 #include <random>
+#include <cstdint>
 
 int main()
 {
   std::random_device seed_gen;
-  std::default_random_engine engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::default_random_engine engine(seed);
 
   std::bernoulli_distribution dist(0.5);
 

reference/random/binomial_distribution.md

@@ -76,11 +76,13 @@ namespace std {
 ```cpp example
 #include <iostream>
 #include <random>
+#include <cstdint>
 
 int main()
 {
   std::random_device seed_gen;
-  std::default_random_engine engine(seed_gen());
+  std::uint32_t seed = seed_gen();
+  std::default_random_engine engine(seed);
 
   // 成功確率0.5の事象を5回試行する
   std::binomial_distribution<> dist(5, 0.5);