fix of sample code

Author: rotarymars

reference/atomic/atomic/fetch_fmaximum.md

@@ -41,9 +41,9 @@ constexpr T
 
 int main()
 {
-  std::atomic<int> x(2);
+  std::atomic<double> x(2);
 
-  int ret = x.fetch_fmaximum(3);
+  double ret = x.fetch_fmaximum(3);
 
   std::cout << ret << std::endl;
   std::cout << x.load() << std::endl;

reference/atomic/atomic/fetch_fmaximum_num.md

@@ -41,9 +41,9 @@ constexpr T
 
 int main()
 {
-  std::atomic<int> x(2);
+  std::atomic<double> x(2);
 
-  int ret = x.fetch_fmaximum_num(3);
+  double ret = x.fetch_fmaximum_num(3);
 
   std::cout << ret << std::endl;
   std::cout << x.load() << std::endl;

reference/atomic/atomic/store_fmaximum.md

@@ -64,7 +64,7 @@ constexpr void
 
 int main()
 {
-  std::atomic<int> x(2);
+  std::atomic<double> x(2);
 
   x.store_fmaximum(3);
 

reference/atomic/atomic/store_fmaximum_num.md

@@ -64,7 +64,7 @@ constexpr void
 
 int main()
 {
-  std::atomic<int> x(2);
+  std::atomic<double> x(2);
 
   x.store_fmaximum_num(3);
 

reference/atomic/atomic/store_fminimum.md

@@ -64,7 +64,7 @@ constexpr void
 
 int main()
 {
-  std::atomic<int> x(2);
+  std::atomic<double> x(2);
 
   x.store_fminimum(3);
 

reference/atomic/atomic/store_fminimum_num.md

@@ -64,7 +64,7 @@ constexpr void
 
 int main()
 {
-  std::atomic<int> x(2);
+  std::atomic<double> x(2);
 
   x.store_fminimum_num(3);