CS 330: Lecture 38 – Automatic Test Running Via Metaprogramming
Dear students, Last time we saw how we could add a hook in Ruby so that when a non-existent method is called on a object, we can still execute the desired action. method_missing lets us write really virtual methods—ones that don’t even exist. Our code effectively used information about the method that would have been […]
CS 330: Lecture 37 – Object-relational Mapping Via Metaprogramming
Dear students, Metaprogramming is our theme for this last week of the semester. What is metaprogramming? It’s when code generates code. It’s when user input is used to generate new classes, methods, and so on. You’ll probably all felt at certain points that the code you are writing probably didn’t need to be written by […]
CS 318: Final Presentations
Dear students, This week we close out the semester with client project presentations. During each presentation, each audience member will write down feedback for the presenter on a quarter-sheet of paper. Here are some topics to address: How effectively did the speaker communicate about the client and purpose of the site? How was time used […]
CS 330: Lecture 36 – Taming Recursion
Dear students, We’ve seen that Haskell does some pretty crazy things: it infers types, it supports this crazy pattern matching stuff, it disallows side effects, and it computes things lazily. Let’s look at one last crazy thing it does: it uses recursion for everything! There are no loop control structures. Normally, when you think of […]
CS 330: Lecture 35 – Call-by-need
Dear students, Last time we introduced a different way of passing parameters. Instead of eagerly evaluating them, we delayed evaluation until they were referenced inside the function. We looked at two examples of delaying evaluation: C preprocessor macros and writing our own control structures. I want to discuss the first of these a little bit […]
CS 330: Lecture 34 – Call-by-name
Dear students, When you call a function, what happens? In particular, what happens in this code? int m() { cout << "m" << std::endl; return 5; } int r() { cout << "r" << std::endl; return 7; } int multiply(int a, int b) { cout << "*" << std::endl; return a * b; } int […]
CS 330: Lecture 33 – Closures Continued
Dear students, Last time we ended in the middle of a discussion about the dangers of closures oversharing values. We fixed the situation by adding a function to introduce a new scope for each closure so they wouldn’t clobber each others’ state. This situation happens frequently enough in Javascript that there’s a slightly simpler idiom […]
CS 330: Lecture 32 – Closures
Dear students, Let’s start with a Program This! Consider the foreach algorithm: for each item in list do something with that item (call a method, print, etc.) The core idea is that we have a list of items, and we want to produce some side effect for each of them. The foreach algorithm doesn’t return […]
CS 318: Lab 22 – Flexbox
Dear students, Today we hit up the new Flexbox system of CSS. In short, Flexbox allows us to control the distribution, alignment, order, and expansion of a bunch children within their parent. It replaces many of the hacks of float and Javascript to achieve certain layouts. We’re going to dive right into the lab today. […]
CS 330: Lecture 31 – HOFs and Lambdas in Java
Dear students, Is Haskell the only language that supports composition and higher-order functions? No. Does Java? It can be made to! Let’s do that today. We start by porting the . operator. What do you suppose the type signature of . is in Haskell? Well, it takes in two functions and gives back a new […]