From 95ef4f720d4dc7c982369e365dbdfcf901ada3ff Mon Sep 17 00:00:00 2001
From: Alex Hirsch <w4rh4wk@bluephoenix.at>
Date: Thu, 22 Oct 2020 12:46:23 +0200
Subject: [PATCH] Exercises: Add task0[45]

---
 exercises/README.md             | 22 ++++++++++++++++++++++
 exercises/task04/iterations.cpp | 19 +++++++++++++++++++
 exercises/task05/strange.cpp    | 23 +++++++++++++++++++++++
 3 files changed, 64 insertions(+)
 create mode 100644 exercises/task04/iterations.cpp
 create mode 100644 exercises/task05/strange.cpp

diff --git a/exercises/README.md b/exercises/README.md
index a391f3d..46e56fa 100644
--- a/exercises/README.md
+++ b/exercises/README.md
@@ -43,3 +43,25 @@ It depends on all three libraries.
 
 CMake itself is a build system generator.
 You can choose from a variety of target build systems.
+
+## Task 04
+
+Examine the program [`iterations.cpp`](task04/iterations.cpp) and think about the expected output.
+Compile the program and run it.
+What do you notice?
+Did you expect this behaviour?
+Did you get any compiler warnings?
+Investigate what is actually happening (consider using `valgrind` or a debugger).
+
+How can such errors be prevented?
+Look for tools (e.g. static code analysers) which help discovering such faulty code.
+
+**Note:** If you run the executable and everything seems normal, try changing the initial content of `xs`, using different optimisation flags, or a different compiler.
+The actual behaviour of this executable depends on various factors.
+
+## Task 05
+
+You are given the program [`strange.cpp`](task05/strange.cpp).
+Compile it with different compilers and optimisation flags.
+What do you notice?
+What is really happening here?
diff --git a/exercises/task04/iterations.cpp b/exercises/task04/iterations.cpp
new file mode 100644
index 0000000..b49ff9e
--- /dev/null
+++ b/exercises/task04/iterations.cpp
@@ -0,0 +1,19 @@
+#include <iostream>
+#include <vector>
+
+int main()
+{
+	std::vector<int> xs{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+
+	for (auto it = xs.begin(); it != xs.end(); ++it) {
+		for (int i = 0; i < *it; i++) {
+			xs.push_back(*it);
+		}
+	}
+
+	std::cout << "Vector: ";
+	for (const auto &x : xs) {
+		std::cout << x << " ";
+	}
+	std::cout << "\n";
+}
diff --git a/exercises/task05/strange.cpp b/exercises/task05/strange.cpp
new file mode 100644
index 0000000..881d8f9
--- /dev/null
+++ b/exercises/task05/strange.cpp
@@ -0,0 +1,23 @@
+#include <iostream>
+
+int array[5] = {};
+
+bool contains(int v)
+{
+	for (int i = 0; i <= 5; ++i) {
+		if (array[i] == v) {
+			return true;
+		}
+	}
+	return false;
+}
+
+int main()
+{
+	for (int i = 0; i < 10; ++i) {
+		auto contains_text = contains(i) ? "contains " : "does not contain ";
+		std::cout << "array " << contains_text << i << std::endl;
+	}
+
+	std::cout << "done" << std::endl;
+}