From c552084f59c8c96cd47e43b220ff8decf457f005 Mon Sep 17 00:00:00 2001
From: tobiglaser <76131623+tobiglaser@users.noreply.github.com>
Date: Wed, 13 Apr 2022 23:05:54 +0200
Subject: [PATCH] Create ReadMe (Worksheet 1 finished)
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+# Computer Science 3 Lab Exercises C++
+
+This repo documents the transition of the third CS3 lab exercises from Java to C++.
+The Course is about programming concepts rather than a specific language.
+
+## Changes
+
+### Worksheet 1
+**Element:**
+ - In Element every mention of Element is replaced with `std::shared_ptr<Element>`.
+ - Command cmd becomes `std::shared_ptr<Command>`.
+ - In the constructor `Element(Command cmd)` uses `std::make_shared<Command>(cmd)` to produce a `std::shared_ptr`.
+ - The destructor `~Element()` may be configured to log destruction of removed Elements.
+
+**CommandList:**
+ - the `Element root` now is a `shared_ptr<Element>` and is initialized inline with `std::make_shared<Element>(Command("root"))`. This is necessary because a shared pointer is empty upon construction.
+ - All member functions previously returning `Command`s now return `std::make_shared<Command>`.
+ This is to allow for returning `nullptr` if something went wrong.
+ - `getElement()` now returns `std::shared_ptr<Element>`.
+ - `getPos()` now returns `std::make_shared<Command>`.
+ - Where appropriate the funtion parameter `int` has been replaced with `unsigned int` to prohibit passing negative values.
+ - In `add(Command cmd)` `std::make_shared<Element>(cmd)` is used to create a new `Element`.
+ Here is easily visible how std::make_shared<T>() is the C++ equivalent to Java`s `new` operator.
+ - The `std::bad_alloc`-Exception possibly thrown by `std::make_shared<Element>()` is not catched in `add()`, to not introduce `try{} catch{}` too early.
+ Thus add() wont return `nullptr`, but crash the program if an error occures.
+
+
+## Trivia
+
+### smart pointers
+ - smart pointers point to NULL on construction.
+ - They can easily be checked for content with
+ ```
+ if (mySmartPointer)
+ //has content
+ else
+ //is empty
+ ```
+ - A unique pointer will be destroyed at the end of it's scope.
+ - A smart pointer will be destroyed when all of it's references are overwritten or the scope of the last reference ends.
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