This scala-lang.org documentation page shares a good reason to use “sealed” traits and classes: When you created sealed traits, the compiler can easily tell all of the subtypes of your class or trait, and as just one benefit, you don’t need to add a default, “catch-all” case in your Scala match expressions.
I originally wrote a long introduction to this article about Scala Options, but I decided to keep that introduction for a future second article in this series. For this article I’ll just say:
Option, Some, and NoneOption valuesmap, filter, fold, and many others are the cure for that verbosityScala FAQ: How can I use regular expression (regex) pattern matching in a match expression (a Scala match/case expression)?
As I wrote in my Scala sed class post earlier today, Jon Pretty’s Kaleidoscope project lets you use string pattern-matching code in Scala match expressions. This enables regex pattern-matching code like this:
A few times during the past year I got tired of trying to remember the Unix/Linux sed syntax while wanting to make edits to many files, so this weekend I wrote a little sed-like Scala class.
If you’re using Java or Scala and need to write a pattern that matches a range of characters, where those characters occur between a minimum and maximum number of times in the pattern, the following example shows a solution I’m currently using.
The idea is that the pattern "[a-zA-Z0-9]{1,4}" means, “Match a string that has only the characters a-z, A-Z, and 0-9, where those characters occur a minimum of one time and a maximum of four times.” The following tests in the Scala REPL shows how this works:
I don’t remember exactly why I wrote this Scala shell script, but if I remember right I was having a problem getting sed to work properly, so I wrote this little script to insert an Amazon Kindle “break” tag before each <h1> tag in an HTML file:
As a brief note about the Linux/Unix sed command, today I learned how to append multiple lines of text to an HTML (or XML) file on macOS. The short answer is that I created a sed commands file named changes.sed with these contents:
This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 1.9, “Extracting Parts of a String that Match Patterns.”
You want to extract one or more parts of a Scala String that match the regular-expression patterns you specify.
Define the regular-expression (regex) patterns you want to extract, placing parentheses around them so you can extract them as “regular-expression groups.” First, define the desired pattern:
This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 1.7, “Finding Patterns in Scala Strings.”
You need to determine whether a Scala String contains a regular expression pattern.