Tyson's blog

Actorsactors again! Stock Trader Example Simulate stock changing prices and a trader purchasing stocks Stock Receives a Tick message and changes its price Price changes are random for this simulation Tick messages are sent to all stocks at regular intervals Receives a GetPrice message and responds with its current price Trader Knows each stock’s ticker symbol and actor reference Receives a CheckStocks message and checks the price of all known stocks Receives Price messages from stock ...

Testing Actorstesting the actors:) Traits and Mixins We’ve seen inheritance by extending abstract class What if we want to extend multiple classes? Example: You want an object class that extends PhysicalObject to have physics applied and extend Actor to run concurrently This is not allowed Can avoid this need by using composition Make a class that extends actor and stores a PhysicalObject in a state variable Traits Similar to abstract classes Cannot have a constructor No limit to the n ...

Concurrency and Actorsnew chapter :) Concurrency Most programs we’ve written execute code sequentially Each statement of code is executed in the order they are written Can have control flow to decide which statements are executed and in which order What if we want multiple pieces of code to execute at the same time? We’ve written 2 types of concurrent software already In CSE115, you wrote a web server What if 2 users are visiting your site at the same time? Server waits for requests and ha ...

Pathfinding with BFSlittle hard :/, but just a little:) Paths Path: A sequence of nodes with each adjacent pair of nodes connected by an edge The length of a path is the number of edges it contains (number of nodes - 1) [LINCOLN, MIT, UTAH, SDC, RAND, UCSB, SRI] <– Path of length 6 Distance Distance between two nodes: The lenght of the shortest path between the nodes Distance between LINCOLN and SRI == 3 [See the video] Distance between RAND and BBN == 1 [See the ...

GraphsIt has cycle, so you know: tree + cycle :/ Data Structures: Review Sequential Data Structures Elements stored in a specific order Ex: Array, List Key-Value Store Stores pairs of elements with no particular order Each key is associated with one value Ex: Map, Dictionary, Object Tree Non-linear structure Each element can be associated with multiple other elements Data Structures How do we store datat with multiple interconnected associations? A [station, intersection, city] ...

Binary Search Tree (BST)Sorted Tree :/ BST - Definition For each node: All values in the left subtree are less than the node’s value All values in the right subtree are greater than the node’s value Duplicate values handled differently based on implementation Sometims not allowed at all BST - Code To make the BST generic Take a type poarameter Take a comparator to decide the sorted order Store a reference to the root node 1234567class BinarySearchTree[A](comparator: (A, A) => B ...

Binary Trees and TraversalsYou would also learn this on CSE191 @.@ Binary Trees Similar in structure to Linked List Consists of Nodes A Tree is only a reference to the first node (Called the root node) Trees have 2 references to nodes Each node has left and right reference Vocab: These are called its child nodes Vocab: The node is the parent to these children The Code123class BinaryTreeNode[A](var value: A, var left: BinaryTreeNode[A], var right: BinaryTreeNode[A]) {} 1234567 ...

Stack and Queue Date structures with specific purposes Restricted features All operations are very efficient Inefficient operations are not allowed We’ll se a stack and queue using linked liss *Scala has builtin Stack and Queue classes Stack LIFO Last in First out The last element pushed onto the stack is the first element to be popped off the stack Only the element on the top of the stack can be accessed Stack Methods Push Add an element to the top of the stack Pop Remove the top elem ...

Linked ListList “Pro” version:) Recall - Array Sequential One continuous block of memory Random access based on memory address address = first_address + (element_size * index) Fixed Size Since memory adjacent to the block may be used Efficient when you know many elements you’ll need to store Array Arrays are stored on the heap Pointer to index 0 goes on the stack add index * sizeOfElement to 1503 to find each element This is called random access Recall - Linked List Sequential S ...

Immutability Immutable Objects Values stored in state variables cannot change Immutable objects are stored on the heap just like any other object But we don’t worry about the state changing when we pass the reference to a method / function What if an immutable object needs to change state? Create a copy of the object with the change applied This ImmutableCounter class takes an initial value in its constructor and has methods to increment and decrement this value The internal Int is ...