Clojure: flattening key paths
This article will cover how to flatten the nested key paths of a map in Clojure. Turning a nested map like {:a {:b {:c {:d 1} :e 2}}} into a flat map like {:a-b-c-d 1 :a-b-e 2}.
@ 2019. All rights reserved
@ 2019. All rights reserved
This article will cover how to flatten the nested key paths of a map in Clojure. Turning a nested map like {:a {:b {:c {:d 1} :e 2}}} into a flat map like {:a-b-c-d 1 :a-b-e 2}.
Clojure provides a powerful namespace for manipulating HTML/XML called clojure.zip. It uses the concept of functional zipper (see Functional Pearls The zipper) to make manipulating hierarchical data structures simple and efficient. This article will cover how to use zippers to manipulate HTML/XML in Clojure.
A tuple is a finite ordered sequence of elements. A common use of tuples in Clojure is for representing pairs of data that are related. For example a key and a value when mapping over a map (hashmap/dictionary). That being said tuples can be of any length, and are a common way of representing larger sets of related data in languages that don't use maps as prolifically as Clojure. This articles explores sorting tuples in Clojure.
HTML and XML are ubiquitous, whether it's the pages of a static site or configuration for a logger, being able to programmatically generate these files can be really powerful. This article will cover how to generate HTML and XML files in Clojure.
Java 8 introduced java.time to replace the existing java representations of time java.util.Date, java.sql.Timestamp etc. There were many problems with this old implementation: it wasn't thread safe, it had a clunky API and no built in representation for timezones. java.time is the successor to the fantastic joda.time project which solves all these problems. So if java.time fixes everything then why this article? Well, java.sql.Timestamp still rears its ugly head at the database layer where it is still the default representation of time in the java.jdbc database drivers. In this article we will cover how to automate the conversion between java.sql.Timestamp and java.time so you never have to deal with java.sql.Timestamp again.
Connection pooling is a technique for improving app performance. A pool (cache) of reusable connections is maintained meaning when users connect to the database they can reuse an existing connection. When the user finishes using the connection it is placed back in the pool for other users to use. This reduces the overhead of connecting to the database by decreasing network traffic, limiting the cost of creating new connections, and reducing the load on the garbage collector. Effectively improving the responsiveness of your app for any task that requires connecting to the database.
Sometimes your problem domain requires the use of emoji. This article will cover how emoji are represented in Clojure strings.
This article will cover how to make a debug macro using tap. See this article for an introduction to Clojure 1.10's tap system.
Clojure 1.10 introduced a new system called tap. From the release notes: tap is a shared, globally accessible system for distributing a series of informational or diagnostic values to a set of (presumably effectful) handler functions. It can be used as a better debug prn, or for facilities like logging etc.
Sometimes web responses contain an unordered sequence of items along with a separate manifest that specifies the ordering. This article will cover how you can write a function to sort the list of items by the manifest order as well as using Clojure Spec to generate test data to verify its output.