std::set hello world example

README.adoc

@@ -14068,6 +14068,8 @@ Programs under link:userland/cpp/[] are examples of https://en.wikipedia.org/wik
 ** link:userland/cpp/temporary_directory.cpp[]: illustrates `std::filesystem::temp_directory_path` and answers https://stackoverflow.com/questions/3379956/how-to-create-a-temporary-directory-in-c/58454949#58454949
 * random
 ** link:userland/cpp/random.cpp[]
+* containers
+** link:userland/cpp/set.cpp[]: `std::set` contains unique keys
 
 [[cpp-multithreading]]
 ==== C++ multithreading
@@ -18701,7 +18703,7 @@ Notably, global monitor operations on memory accesses of regions marked by <<arm
 
 This is done to allow spinlocks opens to automatically wake up WFE sleeping cores at free time without the need for a explicit SEV.
 
-In the shown in the `wfe_ldrex_strex.cpp` example, which can only terminate in gem5 user mode simulation because due to this event.
+In the shown in the `wfe_ldxr_stxr.cpp` example, which can only terminate in gem5 user mode simulation because due to this event.
 
 Note that that program still terminates when running on top of the Linux kernel as explained at: <<wfe-from-userland>>.
 

userland/cpp/set.cpp

@@ -0,0 +1,39 @@
+// https://cirosantilli.com/linux-kernel-module-cheat#cpp
+
+#include <cassert>
+#include <set>
+
+int main() {
+    std::set<int> s{0, 2};
+
+    // Insert another element.
+    auto insert_ret = s.insert(3);
+    assert(insert_ret.first == s.find(3));
+    assert(insert_ret.second == true);
+
+    // Insert something already there, second of return is false.
+    insert_ret = s.insert(3);
+    assert(insert_ret.second == false);
+
+    // Check if a value is present.
+    auto zero = s.find(0);
+    assert(zero != s.end());
+    assert(*zero == 0);
+
+    // Now for a value that is not present.
+    auto one = s.find(1);
+    assert(one == s.end());
+
+#if __cplusplus > 201703L
+    // In C++20 we finally have a .contains() to avoid the end mess!
+    assert(s.contains(0));
+    assert(!s.contains(1));
+#endif
+
+    // Remove an element.
+    // Was present, so return 1;
+    assert(s.erase(0) == 1);
+    assert(s.find(0) == s.end());
+    // Not present, return 0.
+    assert(s.erase(0) == 0);
+}