From 0cb0c373f62fc9baf593642cade5ad8e0213aacd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ciro=20Santilli=20=E5=85=AD=E5=9B=9B=E4=BA=8B=E4=BB=B6=20?=
 =?UTF-8?q?=E6=B3=95=E8=BD=AE=E5=8A=9F?= <ciro.santilli@gmail.com>
Date: Wed, 8 Jan 2020 00:00:00 +0000
Subject: [PATCH] std::set hello world example

---
 README.adoc          |  4 +++-
 userland/cpp/set.cpp | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 userland/cpp/set.cpp

diff --git a/README.adoc b/README.adoc
index 30cd573..63eb272 100644
--- a/README.adoc
+++ b/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>>.
 
diff --git a/userland/cpp/set.cpp b/userland/cpp/set.cpp
new file mode 100644
index 0000000..f219930
--- /dev/null
+++ b/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);
+}