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+{
+ "cells": [
+ {
+ "cell_type": "markdown",
+ "id": "5de78ecc-bbde-49ff-b618-b8c8c440ce47",
+ "metadata": {},
+ "source": [
+ "# Fortgeschrittene Datentypen"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "8ffb53e2-1813-4fdf-962e-e066bc9b737c",
+ "metadata": {},
+ "source": [
+ "## Zuordnungstabellen (assoziative Listen)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "548487ed-dc9d-4404-a2ab-451c0ea742e4",
+ "metadata": {},
+ "source": [
+ "Eine Zuordnungstabelle enthält eine Sammlung von Indizes, die als Schlüssel bezeichnet werden, und eine Sammlung von Werten. Jeder Schlüssel ist mit einem einzigen Wert verbunden. Die Zuordnung eines Schlüssels und eines Wertes wird als Schlüssel-Wert-Paar oder manchmal als Element bezeichnet.\n",
+ "\n",
+ "Die Funktion `Dict` erstellt ein neues Wörterbuch ohne Elemente. Da `Dict` der Name einer integrierten Funktion ist, sollte man vermeiden ihn als Variablenname zu verwenden."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "59ae8d17-a6f6-4210-95bc-0e7492bc8a7a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de = Dict()"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "28490ea3-c4d3-4e4d-915f-612ad36c9472",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de[\"one\"] = \"ein\";"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "09b62b4d-748b-4e1d-91f2-7db610ad02ac",
+ "metadata": {},
+ "source": [
+ "Du kannst auch eine Zuordnungstabelle mit Elementen wie folgt initialisieren:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "92fc203b-4ba8-432a-a541-c4ccf3292195",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de = Dict(\"one\" => \"ein\", \"two\" => \"zwei\", \"three\" => \"drei\")"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "809e7c99-22f0-4440-921d-e5904cadc8a4",
+ "metadata": {},
+ "source": [
+ "Wörterbücher sind veränderbar, was bedeutet, dass es immer möglich ist, ihre Elemente zu ändern, neue Schlüssel-Wert-Paare hinzuzufügen oder bestehende zu entfernen."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "22b295dc-994e-4bbc-ac8d-da5ab9e73493",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de[\"four\"] = \"VIER\"\n",
+ "@show eng2de\n",
+ "eng2de[\"four\"] = \"vier\"\n",
+ "@show eng2de\n",
+ "delete!(eng2de, \"four\")\n",
+ "@show eng2de;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "d8b4ee03-5592-4567-883b-e0842fefeff4",
+ "metadata": {},
+ "source": [
+ "Im Allgemeinen ist die Reihenfolge der Schlüssel-Wert-Paare unvorhersehbar. Dies ist jedoch nicht wichtig, da die Werte immer mithilfe der Schlüssel abgerufen werden."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "e9e4c5b9-9539-4294-a6ec-0a29fb76bf7b",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de[\"two\"]"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "84cf8b52-f061-4b28-a327-bc527820517c",
+ "metadata": {},
+ "source": [
+ "Wenn der Schlüssel nicht im Wörterbuch vorhanden ist, tritt eine Fehlermeldung auf:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "8221269b-7a8f-4cfd-ab8e-0aa4fd6c962d",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de[\"four\"]"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "f83d51c5-2c1d-4449-8cd5-e80f224b9a76",
+ "metadata": {},
+ "source": [
+ "Die Funktion `length` funktioniert auch bei Zuordnungstabellen; sie gibt die Anzahl der Schlüssel-Wert-Paare zurück:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "0e242667-b921-4242-bdcc-cbcac14909b2",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "length(eng2de)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "b4ac7b46-9fc0-47fd-b6c0-c97791517b51",
+ "metadata": {},
+ "source": [
+ "Die Funktion `keys` gibt eine Sammlung mit den Schlüsseln des Wörterbuchs zurück:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "3236f973-d3fa-42ba-a1c0-41e0002446cb",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "keys(eng2de)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "f9bc6fe5-3f7a-458e-942a-11bd3e83dcc6",
+ "metadata": {},
+ "source": [
+ "Nun kannst du den Operator `∈` verwenden, um zu sehen, ob etwas als Schlüssel im Wörterbuch vorhanden ist:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "1fdeb10c-0d84-4c22-b734-d68e2eafe375",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "@show \"one\" ∈ keys(eng2de)\n",
+ "@show \"four\" ∈ keys(eng2de);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "864d141e-6cd2-45e6-95fe-e84cca35cf70",
+ "metadata": {},
+ "source": [
+ "Um zu überprüfen, ob etwas als Wert in einem Wörterbuch vorhanden ist, kannst du die Funktion `values` verwenden, die eine Sammlung von Werten zurückgibt, und dann den Operator `∈` verwenden:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "ab90dad1-61d0-4dbd-b829-a354c13fcb71",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "@show \"ein\" ∈ values(eng2de)\n",
+ "@show \"vier\" ∈ values(eng2de);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "5b255b31-8aca-49b4-a95f-302c59baa975",
+ "metadata": {},
+ "source": [
+ "### Schleifen über Zuordnungstabellen\n",
+ "\n",
+ "Du kannst die Schlüssel der Zuordnungstabelle in einer `for`-Schleife durchlaufen."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "e7062d3f-2125-4ecd-ab13-d04944a71fe1",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function print_dictionary(dic)\n",
+ " for key in keys(dic)\n",
+ " println(key, \" \", dic[key])\n",
+ " end\n",
+ "end\n",
+ "\n",
+ "print_dictionary(eng2de)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "a6b3285a-58f6-41b6-8755-2732a367424e",
+ "metadata": {},
+ "source": [
+ "Auch hier sind die Schlüssel in keiner bestimmten Reihenfolge. Um die Schlüssel in alphabetisch sortierter Reihenfolge zu durchlaufen, kannst du `sort` und `collect` kombinieren:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "6d52aeba-3c7e-405c-bcfe-d76e37e94f51",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function print_dictionary_sorted(dic)\n",
+ " for key in sort(collect(keys(dic)))\n",
+ " println(key, \" \", dic[key])\n",
+ " end\n",
+ "end\n",
+ "\n",
+ "print_dictionary_sorted(eng2de)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "964165ee-4d0d-4122-b6b2-d3926101cab2",
+ "metadata": {},
+ "source": [
+ "### Übung\n",
+ " - Schreibe eine Funktion, die bei Eingabe eines Strings zählt, wie oft jeder Buchstabe vorkommt. Verwende ein Wörterbuch."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "aba1978b-e675-48a7-89aa-75553db70537",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "0acaa2f9-372c-4a3e-be01-27cfe2853fdb",
+ "metadata": {},
+ "source": [
+ "## Tupel und benannte Tupel"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "68ea4303-ce3c-4647-8e9f-89afd0a6a670",
+ "metadata": {},
+ "source": [
+ "Ein Tupel ist eine Sequenz von Werten. Die Werte können beliebigen Typs sein und sie werden durch Ganzzahlen indexiert. Die Tupel sind unveränderlich und jedes Element kann seinen eigenen Typ haben."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "8502cf2e-8bea-4707-811c-f4e6e1de3c8f",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = 'a', 'b', 'c', 'd', 'e'"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "2632b11b-de4b-4f21-bcc6-06a32517c121",
+ "metadata": {},
+ "source": [
+ "Obwohl es nicht notwendig ist, ist es üblich, Tupel in Klammern zu setzen:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "bfa31b99-bf9d-49bb-babc-fe8a65248429",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = ('a', 'b', 'c', 'd', 'e')"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "86fa8b6b-bbbf-4c9c-a5c0-63b00b2c59cb",
+ "metadata": {},
+ "source": [
+ "Um ein Tupel mit einem einzigen Element zu erstellen, musst du ein abschließendes Komma setzen:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "cb1bea15-2b80-43b2-be8e-27507d550fca",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t1 = ('a',)\n",
+ "@show typeof(t1)\n",
+ "\n",
+ "t2 = ('a')\n",
+ "@show typeof(t2);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "d6f34b5b-2aaa-49db-b2a8-d5891fe33ee1",
+ "metadata": {},
+ "source": [
+ "Eine andere Möglichkeit, ein Tupel zu erstellen, ist die integrierte Funktion `tuple`. Ohne Argument erstellt sie ein leeres Tupel:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "952acafe-ca5d-4b58-8969-224b0fe3a28f",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t3 = tuple()\n",
+ "@show typeof(t3)\n",
+ "\n",
+ "t4 = tuple(1, 'a', π, 12.0)\n",
+ "@show typeof(t4);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "efc3d061-7e93-4863-a802-a7cdb869af7e",
+ "metadata": {},
+ "source": [
+ "Mit dem eckigen Klammern-Operator ist es möglich, auf ein Element zuzugreifen. Beachte, dass in Julia das erste Element, anders als in anderen Programmiersprachen (zum Beispiel C, C++, Python), mit 1 indexiert wird."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "9817c28f-428d-4d5b-8384-608f9b4d763d",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t4[2]"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "17a0f0ee-e03f-4669-a5f1-889d875577d9",
+ "metadata": {},
+ "source": [
+ "Es ist auch möglich, mehrere Elemente mithilfe von Slices zu erhalten."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c48ac07f-3a4e-4bb8-9551-2973ea8d2f9c",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "@show t4[1:3];"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "d0f25a1f-0a4c-4ab4-a339-f5ba64806681",
+ "metadata": {},
+ "source": [
+ "Aber wenn du versuchst, eines der Elemente des Tupels zu ändern, tritt ein Fehler auf:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "cfc94cc9-832c-45d2-85b8-aaf789f33f6a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t4[2] = 'b'"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "d956168e-36e4-4abb-a3d6-3c53a857e78d",
+ "metadata": {},
+ "source": [
+ "Da Tupel unveränderlich sind, kannst du die Elemente nicht ändern."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "6a115819-54fd-4550-b097-59fea3ecb523",
+ "metadata": {},
+ "source": [
+ "Genau genommen kann eine Funktion nur einen Wert zurückgeben, aber wenn der Wert ein Tupel ist, hat dies den gleichen Effekt wie das Zurückgeben mehrerer Werte. Zum Beispiel, wenn du zwei Ganzzahlen teilen und den Quotienten und den Rest berechnen möchtest, ist es ineffizient, zuerst x ÷ y und dann x % y zu berechnen. Es ist besser, beides gleichzeitig zu berechnen.\n",
+ "\n",
+ "Die integrierte Funktion `divrem` nimmt zwei Argumente entgegen und gibt ein Tupel aus zwei Werten zurück, dem Quotienten und dem Rest. Du kannst das Ergebnis als Tupel speichern:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "d1dde137-036f-4b93-8010-13b3e835ebd8",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = divrem(7, 3)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "9cd48d9c-cf1d-4546-a2c0-4bb54a42e1e8",
+ "metadata": {},
+ "source": [
+ "Alternativ können wir die Zuweisung als Tupel verwenden, um die Elemente getrennt zu speichern:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c4969556-7945-43c9-8b96-1ea1032cbb3c",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "q, r = divrem(7, 3)\n",
+ "\n",
+ "@show q r;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "e4177fab-a386-4274-8657-bbc6698ec1e5",
+ "metadata": {},
+ "source": [
+ "### Sammeln und verteilen\n",
+ "\n",
+ "Funktionen können eine variable Anzahl von Argumenten entgegennehmen. Ein Parametername, der mit `...` endet, sammelt die Argumente in ein Tupel. Zum Beispiel nimmt `printall` eine beliebige Anzahl von Argumenten entgegen und gibt sie nacheinander aus:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "43f8c7ad-5ac2-425e-a50f-c45624bb3d8a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function printall(args...)\n",
+ " for arg in args\n",
+ " println(arg)\n",
+ " end\n",
+ "end\n",
+ "\n",
+ "printall(1)\n",
+ "printall(1, 2.0, '3')"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "28b3cd91-bf05-43bc-a253-2bee077a1df1",
+ "metadata": {},
+ "source": [
+ "Das Gegenstück zu \"sammeln\" ist \"verteilen\". Wenn du eine Sequenz von Werten hast und sie als mehrere Argumente an eine Funktion übergeben möchtest, kannst du den Operator `...` verwenden. Zum Beispiel nimmt `divrem` genau zwei Argumente an; es funktioniert nicht mit einem Tupel:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "bf55fc10-8432-41e3-bd6c-2244c8c96513",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = (7, 3)\n",
+ "divrem(t)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "db3cd00d-d41c-4f68-95d4-c4e5b283734a",
+ "metadata": {},
+ "source": [
+ "Wenn du aber das Tupel verteilst, funktioniert es:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "e7df53bc-6b2d-4501-9ca8-61e3cb79eb1a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = (7, 3)\n",
+ "divrem(t...)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "dad5d7bf-0dd5-450b-90f3-7768f2d91c18",
+ "metadata": {},
+ "source": [
+ "### Zuordnungstabellen und Tupel"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "3a38cabd-b056-4140-a75c-e0fa383a2a74",
+ "metadata": {},
+ "source": [
+ "Zuordnungstabellen können als Iteratoren verwendet werden, um die Schlüssel-Wert-Paare zu durchlaufen. Du kannst es in einer `for`-Schleife wie folgt verwenden:\n"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "ed483334-36d0-4700-b178-cd9dc5f12189",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "d = Dict('a'=>1, 'b'=>2, 'c'=>3);\n",
+ "for (key, value) in d\n",
+ " println(key, \" \", value)\n",
+ "end"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "5a012731-cf42-487b-9d02-4a4b1d0475c0",
+ "metadata": {},
+ "source": [
+ "Es ist üblich, Tupel als Schlüssel in Zuordnungstabellen zu verwenden. Zum Beispiel könnte ein Telefonverzeichnis Nachname-Vorname-Paare auf Telefonnummern abbilden. Angenommen, wir haben last, first und number definiert, könnten wir schreiben:"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "e5462d35-fa68-42d8-ba00-c5dd1747c557",
+ "metadata": {},
+ "source": [
+ "`directory[last, first] = number`"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "7bd0a942-de38-4c9e-96df-a786fa814254",
+ "metadata": {},
+ "source": [
+ "### Benannte Tupel"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "2284786f-cb8b-4173-944a-e50d79ceca2d",
+ "metadata": {},
+ "source": [
+ "Benannte Tupel sind ein besonderer Tupeltyp in Julia, bei dem jedem Element ein spezifischer Name zugeordnet ist. Dies ermöglicht es dir, auf Elemente anhand ihrer Namen zuzugreifen, was den Code lesbarer und selbsterklärender macht."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "78fb5959-407a-4128-9287-bb9d455f22dc",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "person = (name = \"Michele\", age = 28, city = \"Stuttgart\")"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "01e99a5c-f331-4ad6-95e0-e403b8ad327b",
+ "metadata": {},
+ "source": [
+ "Benannte Tupel sind unveränderlich, aber es ist möglich, den Inhalt zu aktualisieren oder neue Elemente hinzuzufügen, indem eine neue Version erstellt wird. Zum Beispiel:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "ecd22e07-5ba3-4f11-bc77-d967a6fc3fe8",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "updated_person = (person..., age = 29)\n",
+ "updated_person = (person..., number = \"0711 ...\")"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "70061322-9435-496a-ac0d-c026f41e5936",
+ "metadata": {},
+ "source": [
+ "### Übung\n",
+ " - Schreibe eine Funktion `swap_first_last`, die ein Tupel entgegennimmt und ein neues Tupel zurückgibt, bei dem das erste und das letzte Element vertauscht sind. Tipp: Verwende eine Kombination des `...`-Operators und des Slices `[2:end-1]`.\n"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "3721b654-b182-426d-b799-a69e0b53a550",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "5629a477-5d19-43a2-8bb4-e10b10f2ffde",
+ "metadata": {},
+ "source": [
+ "## Objekte und Strukturen"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "18412e4f-e5fb-4a92-a083-ac2e5b58cde3",
+ "metadata": {},
+ "source": [
+ "Zu diesem Zeitpunkt weißt du bereits, wie man Funktionen verwendet, um Code zu organisieren, und integrierte Typen, um Daten zu organisieren. Der nächste Schritt ist zu lernen, wie man eigene Typen erstellt, um sowohl Code als auch Daten zu organisieren.\n",
+ "\n",
+ "Wir haben viele der integrierten Typen von Julia verwendet; jetzt werden wir einen neuen Typ definieren. Als Beispiel werden wir einen Typ namens Punkt erstellen, der einen Punkt im zweidimensionalen Raum repräsentiert.\n",
+ "\n",
+ "Es gibt verschiedene Möglichkeiten, wie wir Punkte in Julia darstellen könnten:\n",
+ " - Wir könnten die Koordinaten separat in zwei Variablen, x und y, speichern.\n",
+ " - Wir könnten die Koordinaten als Elemente in einem Tupel speichern.\n",
+ " - Wir könnten einen neuen Typ erstellen, um Punkte als Objekte darzustellen.\n",
+ "\n",
+ "Hier werden wir die dritte Option untersuchen."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "270c430a-4157-4e54-bb27-660c4028e5c6",
+ "metadata": {},
+ "source": [
+ "Ein vom Programmierer definierter zusammengesetzter Typ wird auch als Struktur (engl. struct) bezeichnet. Die Strukturdefinition für einen Punkt sieht so aus:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c2e3f646-2d82-46a4-a265-01b919412c6d",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "struct Point\n",
+ " x::Real\n",
+ " y::Real\n",
+ "end"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "6b99219f-70ba-41a7-8c52-e3803a360087",
+ "metadata": {},
+ "source": [
+ "Die Kopfzeile zeigt an, dass die neue Struktur Point genannt wird. Der Körper definiert die Attribute oder Felder der Struktur. Die Point-Struktur hat zwei Felder: x und y.\n",
+ "\n",
+ "Eine Struktur ist wie eine Fabrik zur Erzeugung von Objekten. Um einen Punkt zu erstellen, rufst du Point auf, als wäre es eine Funktion, und übergibst die Werte der Felder als Argumente. Wenn Point als Funktion verwendet wird, wird dies Konstruktor genannt. Der Konstruktor gibt eine Instanz des Objekts zurück.\n"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "197339a2-0d8b-4882-bab2-80ba56410f21",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "p = Point(3.0, 4.0)\n",
+ "@show p;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "e35cbbf5-491e-44ff-b2c0-0cf6a8853083",
+ "metadata": {},
+ "source": [
+ "Die Typangabe (`::Real`) ist optional, kann aber hilfreich sein, um die korrekte Verwendung der Struktur zu erzwingen."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "849f1460-d228-4b22-a797-1077d75d1a2d",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "p = Point(\"a\", 4.0)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "b86615f4-592f-41f7-b9d1-f5d1573cfd86",
+ "metadata": {},
+ "source": [
+ "Die Werte der Felder können mithilfe des `.` Operators abgerufen werden."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "00d090e4-d74d-4fad-ae8b-369c1046e48b",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "@show p.x p.y;\n",
+ "@show distance = sqrt(p.x^2 + p.y^2);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "7c6baa9c-56e2-4595-9e6b-c798d9cea002",
+ "metadata": {},
+ "source": [
+ "Die Werte der Felder können mithilfe des `.` Operators abgerufen werden."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "91bd6248-a358-43e3-90cc-6b8398445aaf",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "p.x = 2"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "48b46edb-b8fd-46ca-a2ec-4aa0acbf6c01",
+ "metadata": {},
+ "source": [
+ "Wenn erforderlich, können veränderbare zusammengesetzte Typen mit dem Schlüsselwort `mutable struct` deklariert werden. Hier ist die Definition eines veränderbaren Punkts:\n"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "804c2c32-7a84-4261-88d8-1bad6ba5e18c",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "mutable struct MPoint\n",
+ " x::Real\n",
+ " y::Real\n",
+ "end\n",
+ "p = MPoint(3.0, 4.0)\n",
+ "p.x = 2.0\n",
+ "@show p;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "06f44f63-bf8e-45f5-9495-006e21fc7560",
+ "metadata": {},
+ "source": [
+ "Eine dritte Option ist es, einige Felder einer unveränderlichen Struktur als veränderbar zu definieren. Zum Beispiel kann eine Zuordnungstabellen innerhalb einer unveränderlichen Struktur geändert werden."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "62cab9ae-5e58-401c-bc93-17720914e530",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "struct Book\n",
+ " title::String\n",
+ " author::String\n",
+ " properties::Dict{String, Any}\n",
+ "end\n",
+ "\n",
+ "book = Book(\"Der Hobbit\", \"J.R.R. Tolkien\", Dict(\"available\" => false))\n",
+ "@show book\n",
+ "book.properties[\"available\"] = true\n",
+ "@show book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "53aa5851-35c2-4dd0-a1e0-b5bc8e21b9f6",
+ "metadata": {},
+ "source": [
+ "Du kannst eine Instanz auf die übliche Weise als Argument übergeben. Zum Beispiel:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "e6113221-0c03-484a-99e0-f7d4fab70f03",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function print_point(p)\n",
+ " println(\"($(p.x), $(p.y))\")\n",
+ "end\n",
+ "print_point(p)"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "d5c6fa9e-c31d-4aff-a3fd-db3449904519",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function print_book(book)\n",
+ " println(\"Title: $(book.title)\")\n",
+ " println(\"Author: $(book.author)\")\n",
+ " available = book.properties[\"available\"]\n",
+ " println(\"Available: $(available)\")\n",
+ "end\n",
+ "print_book(book)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "916562a2-3402-41bb-b15d-01333915df99",
+ "metadata": {},
+ "source": [
+ "Funktionen können Instanzen als Rückgabewerte zurückgeben."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "9c57c9f7-c4fd-4263-a55f-62f123aaaa8a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function find_center(point1, point2)\n",
+ " x = (point1.x + point2.x)/2.0\n",
+ " y = (point1.y + point2.y)/2.0\n",
+ " return Point(x, y)\n",
+ "end\n",
+ "\n",
+ "point1 = Point(0.0, 0.0)\n",
+ "point2 = Point(10.0, 10.0)\n",
+ "\n",
+ "@show find_center(point1, point2);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "4afa9ca0-e6cd-4713-8caa-689c9dfdee42",
+ "metadata": {},
+ "source": [
+ "### Übung\n",
+ "\n",
+ " - Schreibe eine Funktion namens `point_distance`, die zwei Punkte als Argumente entgegennimmt und die euklidische Distanz zwischen ihnen zurückgibt."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "b5957a05-e396-41c3-9b8f-f14f089115ab",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "eecb6161-768e-4ae6-a600-d892894f8824",
+ "metadata": {},
+ "source": [
+ "### Referenzen und Werte\n",
+ "\n",
+ "Jedes Objekt (Instanz einer Struktur) wird an einer bestimmten Speicheradresse gespeichert. Der Operator `===` überprüft, ob zwei Variablen auf die gleiche Speicheradresse des Objekts zeigen. Zum Beispiel"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "ed713d91-17f4-4010-a7d3-d39826cffc97",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "book_copy = book\n",
+ "@show book_copy === book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "582e0ac0-2304-429e-a678-c37ab157d5d6",
+ "metadata": {},
+ "source": [
+ "Das bedeutet, dass jede Änderung, die an `book_copy` vorgenommen wird, auch `book` modifiziert."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "a9c46bac-d234-4616-a604-63bdf03b1393",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "book.properties[\"available\"] = true\n",
+ "book_copy.properties[\"available\"] = false\n",
+ "\n",
+ "@show book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "79339467-8994-4a5c-8987-3420d14cb290",
+ "metadata": {},
+ "source": [
+ "Wenn ein neues, eindeutiges Objekt benötigt wird (mit anderen Worten, eine Kopie nach Wert), können wir die Funktion `deepcopy` verwenden."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c36d23c8-2292-4568-aef4-7416c6f3e538",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "book_copy = deepcopy(book)\n",
+ "@show book_copy === book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "4cc4c096-d856-4d43-8808-94edcd3ad906",
+ "metadata": {},
+ "source": [
+ "Schließlich entspricht der `==` Operator zwischen Strukturen standardmäßig dem `===` Operator, da Julia nicht weiß, wie benutzerdefinierte Strukturen verglichen werden sollen. Es ist jedoch immer möglich, den `==` Operator für unsere benutzerdefinierten Typen neu zu implementieren."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "3372eb89-cde6-4040-aa51-b4e76af97851",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "import Base: ==\n",
+ "\n",
+ "function ==(book1::Book, book2::Book)\n",
+ " return book1.title == book2.title && book1.author == book2.author\n",
+ "end\n",
+ "\n",
+ "@show book_copy == book;\n",
+ "@show book_copy === book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "02b533ba-2325-488a-838b-94cdf5ca25bb",
+ "metadata": {},
+ "source": [
+ "Damit können wir vergleichen, ob zwei Bücher gleich sind, auch wenn es sich um zwei unterschiedliche Instanzen desselben Typs handelt."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "4e457ee2-813a-42a8-8ee0-600bb4b50812",
+ "metadata": {},
+ "source": [
+ "## Reine und unreine Funktionen"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "fb008ae0-a457-45db-8f77-425d56e95b30",
+ "metadata": {},
+ "source": [
+ "Wir haben gesehen, dass es ziemlich praktisch ist, Objekte an Funktionen zu übergeben. Bisher haben wir Funktionen gesehen, die den Inhalt ausgeben oder ein neues Objekt erstellen. Keine dieser Funktionen ändert den Inhalt der Eingabeobjekte.\n",
+ " - Eine Funktion, die die Eingabe nicht ändert, wird auch als **rein** bezeichnet.\n",
+ " - Eine Funktion, die die Eingabe ändert, wird als **unrein** bezeichnet. In Julia werden unreine Funktionen durch Hinzufügen eines `!` als letztem Zeichen des Namens hervorgehoben.\n",
+ "\n",
+ "Betrachten wir eine modifizierte Version des Buchs als Beispiel."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "7f892e07-a601-4cba-b58d-40be9c8e93ab",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "book = Book(\"Der Hobbit\", \"J.R.R. Tolkien\", Dict(\"available\" => true, \"copies_in_stock\" => 10))\n",
+ "@show book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "7dac83b5-1086-4ca9-9b36-827497825be6",
+ "metadata": {},
+ "source": [
+ "Dann könnten wir über eine Funktion nachdenken, die die Datenbank aktualisiert, wenn wir neue Exemplare bestellen."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "04937488-a556-44ad-97be-98b017f293fd",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function order_book!(book, number_of_copies)\n",
+ " if number_of_copies <= 0\n",
+ " return\n",
+ " end\n",
+ " book.properties[\"copies_in_stock\"] += number_of_copies\n",
+ " book.properties[\"available\"] = true\n",
+ "end\n",
+ "\n",
+ "order_book!(book, 5)\n",
+ "@show book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "93bc2e46-8530-4d1e-b7fa-55a74d1831c8",
+ "metadata": {},
+ "source": [
+ "### Übung\n",
+ " - Schreibe eine unreine Funktion `sell_book!`, um das Buchobjekt zu aktualisieren, wenn wir ein Exemplar verkaufen. Die Funktion sollte eine Meldung ausgeben, wenn keine Exemplare verfügbar sind."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "6e79fe95-767d-4b3e-af58-623db6dc0712",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "d5bb0b58-e85e-4edb-80b6-19d2c7d49ac3",
+ "metadata": {},
+ "source": [
+ "## Weitere Übungen"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "15fd6da2-f862-40ef-a58d-5e7be488565f",
+ "metadata": {},
+ "source": [
+ "- Erstelle eine Zeitstruktur, die die Uhrzeit des Tages (Stunde, Minute und Sekunde) speichert. Schreibe eine Funktion, die als Eingabe das Zeitobjekt nimmt und es ausgibt. Schreibe dann eine Funktion, die zwei Zeitobjekte zusammenzählt und ein neues Zeitobjekt zurückgibt. Wenn die Summe mehr als 24 Stunden beträgt, sollte sie wie am nächsten Tag zurückgesetzt werden."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "5335e035-62ee-4d0f-acfc-a9e24ac26d99",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "2e0fde12-1214-4709-a7cb-5ebfaa0af17a",
+ "metadata": {},
+ "source": [
+ "- Erstelle eine benutzerdefinierte Version der `==` Funktion, die überprüft, ob zwei Zeitobjekte identisch sind."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "966d4db1-c95a-4531-8209-a869519599ea",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "4e8c3c1e-14fb-439f-97c7-076196f7e5b4",
+ "metadata": {},
+ "source": [
+ "- Erstelle eine benutzerdefinierte Version der `<` und `<=` Funktionen für Zeitobjekte."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c9b76667-731b-4ec2-aaf4-e94496f65b1a",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "b79aad8c-647e-46d0-9b04-6a77cd219953",
+ "metadata": {},
+ "source": [
+ "- Erstelle eine benutzerdefinierte Version der `>` und `>=` Funktionen für Zeitobjekte."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "7df56050-686e-4a87-aa86-9b7f61315aa2",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ }
+ ],
+ "metadata": {
+ "kernelspec": {
+ "display_name": "Julia 1.9.3",
+ "language": "julia",
+ "name": "julia-1.9"
+ },
+ "language_info": {
+ "file_extension": ".jl",
+ "mimetype": "application/julia",
+ "name": "julia"
+ }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}
diff --git a/2_Advanced_Data_Types_en.ipynb b/2_Advanced_Data_Types_en.ipynb
new file mode 100644
index 0000000000000000000000000000000000000000..5161c0bc3096d70a32d7e34f9e15dea5e2247708
--- /dev/null
+++ b/2_Advanced_Data_Types_en.ipynb
@@ -0,0 +1,1141 @@
+{
+ "cells": [
+ {
+ "cell_type": "markdown",
+ "id": "4fe99eff-729a-4d93-ab82-487e5143bae5",
+ "metadata": {},
+ "source": [
+ "# Advanced Data Types"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "7969b8f9-335a-4bd2-82f7-1d9795234ed5",
+ "metadata": {},
+ "source": [
+ "## Dictionaries"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "ea8518c1-8e1d-4532-8055-e04c3aa3e7c4",
+ "metadata": {},
+ "source": [
+ "A dictionary contains a collection of indices, which are called keys, and a collection of values. Each key is associated with a single value. The association of a key and a value is called a key-value pair or sometimes an item.\n",
+ "\n",
+ "The function `Dict` creates a new dictionary with no items. Because `Dict` is the name of a built-in function, you should avoid using it as a variable name. "
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "59ae8d17-a6f6-4210-95bc-0e7492bc8a7a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de = Dict()"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "28490ea3-c4d3-4e4d-915f-612ad36c9472",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de[\"one\"] = \"ein\";"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "f2aff40c-6dcb-421a-b67f-1662c5bf4702",
+ "metadata": {},
+ "source": [
+ "You can also initialize a dictionary with items as:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "92fc203b-4ba8-432a-a541-c4ccf3292195",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de = Dict(\"one\" => \"ein\", \"two\" => \"zwei\", \"three\" => \"drei\")"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "c52d24af-ec90-4b8c-bdd9-988129a7fa81",
+ "metadata": {},
+ "source": [
+ "Dictionaries are mutable, meaning that it is always possible to modify their elements, add new key-value pairs or removing existing ones."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "22b295dc-994e-4bbc-ac8d-da5ab9e73493",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de[\"four\"] = \"VIER\"\n",
+ "@show eng2de\n",
+ "eng2de[\"four\"] = \"vier\"\n",
+ "@show eng2de\n",
+ "delete!(eng2de, \"four\")\n",
+ "@show eng2de;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "01513ad2-3083-4c89-adca-ccc8a88d93d4",
+ "metadata": {},
+ "source": [
+ "In general, the order of the key-value pairs is unpredictable. However this is not important, as the values are always accessed using the keys."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "e9e4c5b9-9539-4294-a6ec-0a29fb76bf7b",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de[\"two\"]"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "9944dbbd-478b-4ae1-ac89-e16be08a0868",
+ "metadata": {},
+ "source": [
+ "If the key isn’t in the dictionary, you get an exception:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "8221269b-7a8f-4cfd-ab8e-0aa4fd6c962d",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "eng2de[\"four\"]"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "a545abaa-78dc-4625-84e9-03b1c8beaaf8",
+ "metadata": {},
+ "source": [
+ "The `length` function works on dictionaries; it returns the number of key-value pairs:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "0e242667-b921-4242-bdcc-cbcac14909b2",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "length(eng2de)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "8e42655b-f2a0-41f0-be90-015ebfeafdb9",
+ "metadata": {},
+ "source": [
+ "The function `keys` returns a collection with the keys of the dictionary:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "3236f973-d3fa-42ba-a1c0-41e0002446cb",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "keys(eng2de)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "acfa7044-5695-4af8-b4bc-320c8a48a220",
+ "metadata": {},
+ "source": [
+ "Now you can use the `∈` operator to see whether something appears as a key in the dictionary:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "1fdeb10c-0d84-4c22-b734-d68e2eafe375",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "@show \"one\" ∈ keys(eng2de)\n",
+ "@show \"four\" ∈ keys(eng2de);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "986919d6-4f27-4fad-b222-20697bf6af40",
+ "metadata": {},
+ "source": [
+ "To see whether something appears as a value in a dictionary, you can use the function `values`, which returns a collection of values, and then use the `∈` operator:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "ab90dad1-61d0-4dbd-b829-a354c13fcb71",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "@show \"ein\" ∈ values(eng2de)\n",
+ "@show \"vier\" ∈ values(eng2de);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "049c9dfd-1e51-4898-98e5-a4b812d0bba2",
+ "metadata": {},
+ "source": [
+ "### Loops over dictionaries\n",
+ "\n",
+ "You can traverse the keys of the dictionary in a `for` statement."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "e7062d3f-2125-4ecd-ab13-d04944a71fe1",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function print_dictionary(dic)\n",
+ " for key in keys(dic)\n",
+ " println(key, \" \", dic[key])\n",
+ " end\n",
+ "end\n",
+ "\n",
+ "print_dictionary(eng2de)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "cf27195c-e601-49ca-b03d-63162bf59bce",
+ "metadata": {},
+ "source": [
+ "Again, the keys are in no particular order. To traverse the keys in alphabetically sorted order, you can combine `sort` and `collect`:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "6d52aeba-3c7e-405c-bcfe-d76e37e94f51",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function print_dictionary_sorted(dic)\n",
+ " for key in sort(collect(keys(dic)))\n",
+ " println(key, \" \", dic[key])\n",
+ " end\n",
+ "end\n",
+ "\n",
+ "print_dictionary_sorted(eng2de)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "8daa9d3e-19de-4415-ba6c-6aeb174b38fa",
+ "metadata": {},
+ "source": [
+ "### Exercise\n",
+ " - Write a function that given a string as input counts how many times each letter appears. Use a dictionary."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "aba1978b-e675-48a7-89aa-75553db70537",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "3a9b281f-6cc0-4d39-b9e2-d816823f9873",
+ "metadata": {},
+ "source": [
+ "## Tuples and named tuples"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "a722109e-86cc-44e3-9256-a3e93a1668f5",
+ "metadata": {},
+ "source": [
+ "A tuple is a sequence of values. The values can be of any type, and they are indexed by integers. The tuples are immutable and each element can have its own type."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "8502cf2e-8bea-4707-811c-f4e6e1de3c8f",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = 'a', 'b', 'c', 'd', 'e'"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "d01f5647-a240-4620-9a3a-782835aca39c",
+ "metadata": {},
+ "source": [
+ "Although it is not necessary, it is common to enclose tuples in parentheses:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "bfa31b99-bf9d-49bb-babc-fe8a65248429",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = ('a', 'b', 'c', 'd', 'e')"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "3fa935e0-0611-4b8a-982c-329c33a74f99",
+ "metadata": {},
+ "source": [
+ "To create a tuple with a single element, you have to include a final comma:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "cb1bea15-2b80-43b2-be8e-27507d550fca",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t1 = ('a',)\n",
+ "@show typeof(t1)\n",
+ "\n",
+ "t2 = ('a')\n",
+ "@show typeof(t2);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "193457ac-4e4b-4e58-8c28-6d8b4331d532",
+ "metadata": {},
+ "source": [
+ "Another way to create a tuple is the built-in function tuple. With no argument, it creates an empty tuple:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "952acafe-ca5d-4b58-8969-224b0fe3a28f",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t3 = tuple()\n",
+ "@show typeof(t3)\n",
+ "\n",
+ "t4 = tuple(1, 'a', π, 12.0)\n",
+ "@show typeof(t4);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "729c3597-1a35-4a26-ae7a-6dadee31daeb",
+ "metadata": {},
+ "source": [
+ "Using the bracket operator it is possible to access an element. Note, differently from other programming languages (for example C, C++, Python) in Julia the first element is 1."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "9817c28f-428d-4d5b-8384-608f9b4d763d",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t4[2]"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "2519be57-8c10-4878-a772-017b099f6a4c",
+ "metadata": {},
+ "source": [
+ "It is also possible to get multiple elements by using slices."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c48ac07f-3a4e-4bb8-9551-2973ea8d2f9c",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "@show t4[1:3];"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "aeda8602-f9da-4173-a692-54e2e9a0e178",
+ "metadata": {},
+ "source": [
+ "But if you try to modify one of the elements of the tuple, you get an error:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "cfc94cc9-832c-45d2-85b8-aaf789f33f6a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t4[2] = 'b'"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "b9f13b5c-9e61-46b9-a47d-f90199bd7bd2",
+ "metadata": {},
+ "source": [
+ "Because tuples are immutable, you can’t modify the elements."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "a10cb9a7-8f44-44f8-831f-178b780e4ac9",
+ "metadata": {},
+ "source": [
+ "Strictly speaking, a function can only return one value, but if the value is a tuple, the effect is the same as returning multiple values. For example, if you want to divide two integers and compute the quotient and remainder, it is inefficient to compute x ÷ y and then x % y. It is better to compute them both at the same time.\n",
+ "\n",
+ "The built-in function `divrem` takes two arguments and returns a tuple of two values, the quotient and remainder. You can store the result as a tuple: "
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "d1dde137-036f-4b93-8010-13b3e835ebd8",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = divrem(7, 3)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "ea615dbd-effb-4442-b160-20e7c9b6c22e",
+ "metadata": {},
+ "source": [
+ "Alternatively, we can use tuple assignment to store the elements separately:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c4969556-7945-43c9-8b96-1ea1032cbb3c",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "q, r = divrem(7, 3)\n",
+ "\n",
+ "@show q r;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "4574e191-aaa8-4834-8837-54947d6ddf30",
+ "metadata": {},
+ "source": [
+ "### Gather and scatter\n",
+ "\n",
+ "Functions can take a variable number of arguments. A parameter name that ends with `...` gathers arguments into a tuple. For example, `printall` takes any number of arguments and prints them one by line:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "43f8c7ad-5ac2-425e-a50f-c45624bb3d8a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function printall(args...)\n",
+ " for arg in args\n",
+ " println(arg)\n",
+ " end\n",
+ "end\n",
+ "\n",
+ "printall(1)\n",
+ "printall(1, 2.0, '3')"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "eb662374-fe83-49d7-a5be-d9582d037ad1",
+ "metadata": {},
+ "source": [
+ "The complement of gather is scatter. If you have a sequence of values and you want to pass it to a function as multiple arguments, you can use the `...` operator. For example, `divrem` takes exactly two arguments; it doesn’t work with a tuple:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "bf55fc10-8432-41e3-bd6c-2244c8c96513",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = (7, 3)\n",
+ "divrem(t)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "d05def39-3244-4acd-a082-a7ee532f8f1d",
+ "metadata": {},
+ "source": [
+ "But if you scatter the tuple, it works:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "e7df53bc-6b2d-4501-9ca8-61e3cb79eb1a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "t = (7, 3)\n",
+ "divrem(t...)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "2cf01c32-9d1b-4e83-9375-f737e51c58ed",
+ "metadata": {},
+ "source": [
+ "### Dictionaries and Tuples"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "00e97ccc-8e64-4eef-84be-85a266eb3490",
+ "metadata": {},
+ "source": [
+ "Dictionaries can be used as iterators that iterate the key-value pairs. You can use it in a `for` loop like this:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "ed483334-36d0-4700-b178-cd9dc5f12189",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "d = Dict('a'=>1, 'b'=>2, 'c'=>3);\n",
+ "for (key, value) in d\n",
+ " println(key, \" \", value)\n",
+ "end"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "dcb05236-810a-410b-aaa0-0cb431e3e64f",
+ "metadata": {},
+ "source": [
+ "It is common to use tuples as keys in dictionaries. For example, a telephone directory might map from last-name, first-name pairs to telephone numbers. Assuming that we have defined last, first and number, we could write:"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "e5462d35-fa68-42d8-ba00-c5dd1747c557",
+ "metadata": {},
+ "source": [
+ "`directory[last, first] = number`"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "9980d710-392b-4716-b44d-98e6c5c8b838",
+ "metadata": {},
+ "source": [
+ "### Named tuples"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "e514c4bd-c17c-44f4-a89f-88154cc1bf6c",
+ "metadata": {},
+ "source": [
+ "Named tuples are a special type of tuple in Julia where each element has a specific name associated with it. This allows you to access elements by their names, making the code more readable and self-explanatory."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "78fb5959-407a-4128-9287-bb9d455f22dc",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "person = (name = \"Michele\", age = 28, city = \"Stuttgart\")"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "63075b2d-ef86-48e4-8f84-981f81fdece0",
+ "metadata": {},
+ "source": [
+ "Named tuples are immutable, however it is possible to update the content, or to add new elements, by creating a new version. For example:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "ecd22e07-5ba3-4f11-bc77-d967a6fc3fe8",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "updated_person = (person..., age = 29)\n",
+ "updated_person = (person..., number = \"0711 ...\")"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "347fe4ea-5b63-4fb8-91bc-2b7b8a0c6a30",
+ "metadata": {},
+ "source": [
+ "### Exercise\n",
+ " - Write a function `swap_first_last` that takes a tuple and returns a new tuple with the first and last elements swapped. Tip: use a combination of the `...` operator and of this slice `[2:end-1]`."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "3721b654-b182-426d-b799-a69e0b53a550",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "647530cd-480a-414f-a8ec-1375e05a9e1b",
+ "metadata": {},
+ "source": [
+ "## Objects and structs"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "00b9bdb1-86ad-47f6-b8c3-88e85878eaff",
+ "metadata": {},
+ "source": [
+ "At this point you know how to use functions to organize code and built-in types to organize data. The next step is to learn how to build your own types to organize both code and data.\n",
+ "\n",
+ "We have used many of Julia’s built-in types; now we are going to define a new type. As an example, we will create a type called Point that represents a point in two-dimensional space.\n",
+ " \n",
+ "There are several ways we might represent points in Julia:\n",
+ " - We could store the coordinates separately in two variables, x and y.\n",
+ " - We could store the coordinates as elements in an tuple.\n",
+ " - We could create a new type to represent points as objects.\n",
+ "\n",
+ "Here we will investigate the third option."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "9aa53d46-033b-4559-a5d8-e95357a257a5",
+ "metadata": {},
+ "source": [
+ "A programmer-defined composite type is also called a struct. The struct definition for a point looks like this:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c2e3f646-2d82-46a4-a265-01b919412c6d",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "struct Point\n",
+ " x::Real\n",
+ " y::Real\n",
+ "end"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "fb9be134-9730-4dbd-9e05-51dd94e9d8e0",
+ "metadata": {},
+ "source": [
+ "The header indicates that the new struct is called Point. The body defines the attributes or fields of the struct. The Point struct has two fields: x and y.\n",
+ "\n",
+ "A struct is like a factory for creating objects. To create a point, you call Point as if it were a function having as arguments the values of the fields. When Point is used as a function, it is called a constructor. The constructor returns an instance of the object."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "197339a2-0d8b-4882-bab2-80ba56410f21",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "p = Point(3.0, 4.0)\n",
+ "@show p;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "b0134aa7-f356-4d71-9d46-959bd3cfe89a",
+ "metadata": {},
+ "source": [
+ "The type speficication (`::Real`) is optional, but can be helpful to enforce correct usage of the struct."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "849f1460-d228-4b22-a797-1077d75d1a2d",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "p = Point(\"a\", 4.0)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "e3011b23-816d-4aa2-be61-7eb8f4aee9d1",
+ "metadata": {},
+ "source": [
+ "The values of the fields can be accessed using the `.` operator."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "00d090e4-d74d-4fad-ae8b-369c1046e48b",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "@show p.x p.y;\n",
+ "@show distance = sqrt(p.x^2 + p.y^2);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "08748a8c-f76c-4f14-b3d2-9db99fb28e87",
+ "metadata": {},
+ "source": [
+ "Structs are however by default immutable, after construction the fields can not change value:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "91bd6248-a358-43e3-90cc-6b8398445aaf",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "p.x = 2"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "629c1004-5d0f-4093-b546-473c94c91b44",
+ "metadata": {},
+ "source": [
+ "Where required, mutable composite types can be declared with the keyword mutable struct. Here is the definition of a mutable point:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "804c2c32-7a84-4261-88d8-1bad6ba5e18c",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "mutable struct MPoint\n",
+ " x::Real\n",
+ " y::Real\n",
+ "end\n",
+ "p = MPoint(3.0, 4.0)\n",
+ "p.x = 2.0\n",
+ "@show p;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "1bd558dd-e6c3-4dc0-9476-768c59178708",
+ "metadata": {},
+ "source": [
+ "A third option is to let some fields of an unmutable struct to be mutable. For example a dictionary inside an unmutable struct can be modified."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "62cab9ae-5e58-401c-bc93-17720914e530",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "struct Book\n",
+ " title::String\n",
+ " author::String\n",
+ " properties::Dict{String, Any}\n",
+ "end\n",
+ "\n",
+ "book = Book(\"Der Hobbit\", \"J.R.R. Tolkien\", Dict(\"available\" => false))\n",
+ "@show book\n",
+ "book.properties[\"available\"] = true\n",
+ "@show book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "31e2098b-5079-4cb5-bf64-a7a78754af32",
+ "metadata": {},
+ "source": [
+ "You can pass an instance as an argument in the usual way. For example:"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "e6113221-0c03-484a-99e0-f7d4fab70f03",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function print_point(p)\n",
+ " println(\"($(p.x), $(p.y))\")\n",
+ "end\n",
+ "print_point(p)"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "d5c6fa9e-c31d-4aff-a3fd-db3449904519",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function print_book(book)\n",
+ " println(\"Title: $(book.title)\")\n",
+ " println(\"Author: $(book.author)\")\n",
+ " available = book.properties[\"available\"]\n",
+ " println(\"Available: $(available)\")\n",
+ "end\n",
+ "print_book(book)"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "3b12a004-81d9-4bbc-9e2e-d2c281dcbe18",
+ "metadata": {},
+ "source": [
+ "Functions can return instances as return values."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "9c57c9f7-c4fd-4263-a55f-62f123aaaa8a",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function find_center(point1, point2)\n",
+ " x = (point1.x + point2.x)/2.0\n",
+ " y = (point1.y + point2.y)/2.0\n",
+ " return Point(x, y)\n",
+ "end\n",
+ "\n",
+ "point1 = Point(0.0, 0.0)\n",
+ "point2 = Point(10.0, 10.0)\n",
+ "\n",
+ "@show find_center(point1, point2);"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "078b31ab-11e1-4596-8271-f0d33418eab8",
+ "metadata": {},
+ "source": [
+ "### Exercise\n",
+ "\n",
+ " - Write a function called `point_distance` which takes two points as arguments and returns the Euclidean distance between them."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "b5957a05-e396-41c3-9b8f-f14f089115ab",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "attachments": {},
+ "cell_type": "markdown",
+ "id": "0fb1f6bc-e6e5-4897-bbb6-880e40e3bf20",
+ "metadata": {},
+ "source": [
+ "### References and values\n",
+ "\n",
+ "Each object (instance of a struct) is stored at some memory address. The operator `===` checks if two variables point to the same memory address of the object. For example"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "ed713d91-17f4-4010-a7d3-d39826cffc97",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "book_copy = book\n",
+ "@show book_copy === book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "636b6713-f4ed-4220-a159-2918bd44f78e",
+ "metadata": {},
+ "source": [
+ "This means that any change made to `book_copy` will also modify `book`."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "a9c46bac-d234-4616-a604-63bdf03b1393",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "book.properties[\"available\"] = true\n",
+ "book_copy.properties[\"available\"] = false\n",
+ "\n",
+ "@show book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "6bcbf983-40fa-4fc8-8eca-7cd7c45778dc",
+ "metadata": {},
+ "source": [
+ "If a new, distinct, object is needed (in other words, a copy by value), we can use the function `deepcopy`. "
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c36d23c8-2292-4568-aef4-7416c6f3e538",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "book_copy = deepcopy(book)\n",
+ "@show book_copy === book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "02cc3ec7-e712-4c4b-abf5-9bfc98e68a91",
+ "metadata": {},
+ "source": [
+ "Finally, the `==` operator between structs defaults to the `===` operator as Julia has no way of knowing how to compare custom structs. However, it is always possible to reimplement the `==` operator for our custom types."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "3372eb89-cde6-4040-aa51-b4e76af97851",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "import Base: ==\n",
+ "\n",
+ "function ==(book1::Book, book2::Book)\n",
+ " return book1.title == book2.title && book1.author == book2.author\n",
+ "end\n",
+ "\n",
+ "@show book_copy == book;\n",
+ "@show book_copy === book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "87c1e4fb-d4e2-4ada-a97f-61273012146c",
+ "metadata": {},
+ "source": [
+ "With this we can compare if two books are the same, even if they are two distinct instances of the same struct."
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "9263a1ae-52ee-4afc-9d9f-0f1341b64bc0",
+ "metadata": {},
+ "source": [
+ "## Pure and impure functions"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "f638e9b3-9926-46fc-81e0-d49c877a3bbb",
+ "metadata": {},
+ "source": [
+ "We have seen that it is quite convenient to pass objects to functions. So far we have seen functions that print the content or that create a new object. None of these functions are modifying the content of the input objects.\n",
+ " - A function that does not modify the input it is also said **pure**.\n",
+ " - A function which modifies the input it is said **impure**. In Julia impure functions are highlighted by adding a `!` as the last character of the name.\n",
+ "\n",
+ "Let's consider a modified version of the book for an example."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "7f892e07-a601-4cba-b58d-40be9c8e93ab",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "book = Book(\"Der Hobbit\", \"J.R.R. Tolkien\", Dict(\"available\" => true, \"copies_in_stock\" => 10))\n",
+ "@show book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "99f4d6c9-2633-4394-b6a0-e0ce0c05e0db",
+ "metadata": {},
+ "source": [
+ "Then we could think of a function which updates the database whenever we order new copies."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "04937488-a556-44ad-97be-98b017f293fd",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "function order_book!(book, number_of_copies)\n",
+ " if number_of_copies <= 0\n",
+ " return\n",
+ " end\n",
+ " book.properties[\"copies_in_stock\"] += number_of_copies\n",
+ " book.properties[\"available\"] = true\n",
+ "end\n",
+ "\n",
+ "order_book!(book, 5)\n",
+ "@show book;"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "b30bd560-5ff3-4706-9f53-e6a5158651e9",
+ "metadata": {},
+ "source": [
+ "### Exercise\n",
+ " - Write an inpure function `sell_book!` for updating the book object whenever we sell a single copy. The function should complain if there are no copies available."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "6e79fe95-767d-4b3e-af58-623db6dc0712",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "5ed4d4e0-0454-4298-9a56-8fb32634aa24",
+ "metadata": {},
+ "source": [
+ "## Further exercises"
+ ]
+ },
+ {
+ "cell_type": "markdown",
+ "id": "8446f1db-d40f-4311-9597-3b3b4d913151",
+ "metadata": {},
+ "source": [
+ "- Create a time struct which stores the time of the day (hour, minute and second). Write a function which takes as input the time object and prints it. Then write a function which sums together two time objects and returns a new time object. If the total is more than 24 hours, it should reset as if it was the next day."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "5335e035-62ee-4d0f-acfc-a9e24ac26d99",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "32844b6f-518a-4174-83c6-0d7ebeabe4e4",
+ "metadata": {},
+ "source": [
+ " - Create a custom version of the `==` function which checks if two time objects are the same."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "966d4db1-c95a-4531-8209-a869519599ea",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "baa7e06f-e183-4ee7-912a-e22255e18e21",
+ "metadata": {},
+ "source": [
+ " - Create a custom version of the `<` and `<=` functions for time objects."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "c9b76667-731b-4ec2-aaf4-e94496f65b1a",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ },
+ {
+ "cell_type": "markdown",
+ "id": "1bdbd748-7482-4f54-99a7-3d6e74b65575",
+ "metadata": {},
+ "source": [
+ " - Create a custom version of the `>` and `>=` functions for time objects."
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
+ "id": "7df56050-686e-4a87-aa86-9b7f61315aa2",
+ "metadata": {},
+ "outputs": [],
+ "source": []
+ }
+ ],
+ "metadata": {
+ "kernelspec": {
+ "display_name": "Julia 1.9.3",
+ "language": "julia",
+ "name": "julia-1.9"
+ },
+ "language_info": {
+ "file_extension": ".jl",
+ "mimetype": "application/julia",
+ "name": "julia"
+ }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}