Category: Misc Languages

Amuda Adelou shows how to use Tesseract’s Java API to perform character recognition in images:

Extracting text from an image means that you are considering the flowchart imagery that’s processed to extract the text components and then extracting the geometrical shapes components. The text components are extracted with geometrical components, as well. The internal relationship between the components is set up by tracing the flow lines that connect different components. The extracted components are output to metadata (in XML format), which is machine-readable. This metadata can be archived, stored in a knowledge base, or shared with others.

Click through for a demo app and code.

Vladimir Khorikov has an example of removing shared state and making application code more “honest” as a result:

Note how we’ve removed the private fields. Getting rid of the shared state automatically decoupled the three methods and made the workflow explicit. Without the shared state, the only way we can carry data around is by using the methods’ arguments and return values. And that is exactly what we did: all three members now explicitly state required inputs and possible outputs in their signatures.

This is the essence of functional programming. With honest method signatures, it’s extremely easy to reason about the code as we don’t need to keep in mind hidden relationships between its different parts. It’s also impossible to mess up with the invocation order. If we try, for example, to put the second line above the first one, the code simply wouldn’t compile:

This is one of many reasons why I’m fond of functional programming.

Angshuman Talukdar shows how to use neo4j to solve minimum weighted distance problems:

A sample dataset is created in Neo4j using the CREATE clause in Cypher as given in Query 1 (create clause in Cypher). This loads the data into Neo4j and generates the graph database as shown in Figure 2.

Neo4j has a lot of graph algorithms shipped with it as a package and those are accessible only from the JAVA API. Implementing some of these algorithms in Cypher is quite complex and time consuming. From Neo4j 3.x, the concept of user defined procedures had been introduced called APOC (Awesome Procedures On Cypher). Those are custom implementations of certain functionality, that can’t be (easily) expressed in Cypher itself. The APOC library consists of many (about 300) procedures to help with many different tasks in areas like data integration, graph algorithms or data conversion.

Graph databases aren’t common, but they can be very useful for certain questions like the one Angshuman solves.

Matthew Rathbone shows different concurrency options available in Scala:

Scala is a functional programming language that aims to avoid side effects by encouraging you to use immutable variables (called ‘values’), and data structures.

So by default in Scala when you build a list, array, string, or other object, that object is immutable and cannot be changed or updated.

This might seem unrelated, but think about a thread which has been given a list of strings to process, perhaps each string is a website that needs crawling.

In the Java model, this list might be updated by other threads at the same time (adding / removing websites), so you need to make sure you either have a thread-safe list, or you safeguard access to it with the protected keyword or a Mutex.

By default in Scala this list is immutable, so you can be sure that the list cannot be modified by other threads, because it cannot be modified at all.

While this does force you to program in different ways to work around the immutability, it does have the tremendous effect of simplifying thread-safety concerns. The value of this cannot be understated, it’s a huge burden to worry about thread safety all the time, but in Scala much of that burden goes away.

Read the whole thing if you’re looking at writing Spark applications in Scala.  If you’re thinking about functional programming in .NET languages, F# is  there for you.

Chris Koester has a quick-and-easy file reader in a few lines of C#:

This post describes one way that you can read the top N rows from large text files with C#. This is very useful when working with giant files that are too big to open, but you need to view a portion of them to determine the schema, data types, etc.

I’ve used PowerShell many times to do this with large csv files, but in this example we’re going to use C# and look at the Wikipedia XML dump of pages and articles. The 3017-03-01 dump is very large and comes in at 59.5 GB.

I’ve had to write something similar before on Windows machines where I didn’t have access to more/less.  It’s really helpful for perusing the first few lines of gigantic log files.