As a long-time Java dev, it is tempting to declare function parameters as Lists. This is appropriate if we require an ordered sequence, but usually we only care that we can iterate over it. Our functions are more general if they accept any Seq. [1] However, now and then I really miss the cons operator … Read moreScala: when you wish that Seq was a List
Scala’s type system is impressive, and yesterday one feature came in handy: converting certain classes into a common type with useful methods on it. Say several types have a core set of characteristics, and we want to define methods based on those without modifying the original classes. In this example, various classes represent regions of … Read moreDuck typing is like the force
The first tenet of functional programming: code is data. Store it in variables, pass it as parameters, return it from methods. This is challenging in the JVM, where all code lives inside methods on objects. Therefore, Scala passes around code in a function object. Code lives in the apply() method. When is a function object created? … Read moreWhen is code data, and when is it code?
flatMap is a method on collections that, at a surface level, transforms each element into another collection of any type, then takes all the elements out of those collections and puts them into one. It is like a map followed by a flatten. Why do two things in one step? Conceptually, List.map is always 1:1 … Read moreWhat is flatMap?
In the beginning, there were Iterables. And in the old world of Java, they were good. We could perform the advanced for loop on them. for (Thing item : listOfThings) { // do stuff to each item} And we could perform it again and again. for (Thing item : listOfThings) { // do more stuff … Read moreIterators in Scala: glory and danger
When creating a method or procedure in Scala, we start with def, then the name and parameters (if any), optionally the return type, and then the method body. There’s a subtlety here: sometimes the method is equal to the method body, and other times the equals sign is missing. For instance: class Birthday { def … Read moredef in Scala: equals sign or no equals sign?
In Scala, one can define class properties with either “def” or “val.” Using “def“, one can define the property with or without parentheses, and with or without the equal sign. Why is this? What are the consequences? For illustrative purposes, we’ll use a block of code that printing to the console, then returns an int. … Read moreChoices with def and val in Scala
Michael Feathers has a great blog post up today about how object-oriented and functional programming styles are suited to different portions of an application. Specifically, the object-oriented style fits the high-level application components. The original intention of OO was for objects to pass messages to each other, which is suited to a SOA style and … Read moreThe confluence of FP and OO
One of the goals of Scala is increased consistency compared to Java.Here are three high-level consistencies in Scala: Every value is an object. There are no primitives in Scala. Even its version of void (Unit) is an object. Nothing is an object. Nil is an object. Arrays are objects. Everything is an object. Every statement … Read moreConsistency in Scala
In Scala, the “for” structure can throw off the Java programmer. For one, it looks enough like a Java “for” loop for a Java programmer to make a guess on how it works — but that guess is likely to be wrong. For another, the for-loop is implemented in Scala as a special case of … Read moreFor-confusion in Scala