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Vitali Socks
Vitali Socks

Scala: First Thoughts Fix


All of the code used in this post in contained in the first-monads directory of my blog repo. The best way to follow this post is to copy-and-paste commands one-at-a-time from this post to a Scala REPL or sbt console. Note that only the numerical linear algebra examples later in this post require any non-standard dependencies.




Scala: First Thoughts



Here we have ended up with an Option wrapped in another Option, which is not what we want. But we now know the solution, which is to replace the first map with flatMap, or better still, use a for-comprehension.


If you want to get your hands dirty and contribute to Scala 3, now is a good time to get involved! Head to our Getting Started page for new contributors, and have a look at some of the good first issues. They make perfect entry points into hacking on the compiler.


While going through Scala Specification, Topic 3 about Types, I came across this > "We distinguish between first-order types and type constructors, which take type parameters and yield types."With this my assumption is First-order types are parameterized types that takes only one type to be applied and become concrete. ex:List[A] that can take only one argument i.e. Int and become concrete type List[Int], while Type constructors can be of higher order(Higher-kinded Types) like Container[] that can take a List as a Parameter and can be used like:trait Traversable[Container[], T]new Traversable(List, Int) that is going to create a List[Int] that is of Traversable type.


So List is a type constructor. List[Int] is a first-order type. Monad (defined as trait Monad[F[_]]) is a type constructor. Monad[List] is a first-order type.val x: List = ??? is not valid, neither is val x: Monad = ???, but val x: List[Int] = ??? and val x: Monad[List] = ??? do compile.


Spark SQL supports two different methods for converting existing RDDs into Datasets. The firstmethod uses reflection to infer the schema of an RDD that contains specific types of objects. Thisreflection-based approach leads to more concise code and works well when you already know the schemawhile writing your Spark application.


TL;DR: Scala 2 is still the most used version of Scala, according to the Scala Developer survey. This means that context abstractions are still giving headaches to Scala developers, especially newcomers. This blog introduces contextual abstractions, first from a Scala 3 point of view, profiting from the API overhaul. Then we will drive home the intuition of contextual abstractions with some code examples, and conclude with the relationship with Scala 2, thus using the design principles of the Scala 3 contextual abstractions when working on Scala 2 codebases to avoid pitfalls and detect code smells, and also to make it easier to digest.


if(typeof ez_ad_units != 'undefined')ez_ad_units.push([[728,90],'sparkbyexamples_com-box-2','ezslot_8',132,'0','0']);__ez_fad_position('div-gpt-ad-sparkbyexamples_com-box-2-0');In Spark/PySpark, you can use show() action to get the top/first N (5,10,100 ..) rows of the DataFrame and display them on a console or a log, there are also several Spark Actions like take(), tail(), collect(), head(), first() that return top and last n rows as a list of Rows (Array[Row] for Scala). Spark Actions get the result to Spark Driver, hence you have to be very careful when you are extracting large datasets. Collecting large datasets that are larger than Spark Driver memory returns OutOfMemoryError and the job fails.


Note: take(), first() and head() actions internally calls limit() transformation and finally calls collect() action to collect the data.if(typeof ez_ad_units != 'undefined')ez_ad_units.push([[728,90],'sparkbyexamples_com-medrectangle-3','ezslot_5',156,'0','0']);__ez_fad_position('div-gpt-ad-sparkbyexamples_com-medrectangle-3-0');


While working with Python and Spark, we often required to convert Pandas to PySpark DataFrame and vice-versa, you can limit the top n number of records when you convert back to pandas, below code snippet provides an example of getting first 3 records from DataFrame and converted to pandas..if(typeof ez_ad_units != 'undefined')ez_ad_units.push([[336,280],'sparkbyexamples_com-box-4','ezslot_7',139,'0','0']);__ez_fad_position('div-gpt-ad-sparkbyexamples_com-box-4-0');


In this article, you have learned show() is used to get the top first n records from DataFrame, take() and head() are used to get the top first n records, tail() is used to get the last N records as a list of Row (Array[Row] for scala). and also learned limit() is a transformation that is used to get the top N rows as a DataFrame/Dataset.


In 1839 Oberto Conte di San Bonifacio inaugurated the cycle of operas by Giuseppe Verdi (1813-1901), the composer whose name is linked more than any other to the history of La Scala. After the dismal failure of Un giorno di regno, Nabucco was performed in 1842. It was the first, decisive triumph of Verdi's career. At the same time, the strong patriotic feelings stirred by Nabucco founded the "popularity" of opera seria and identified its image with the Scala.


On the outside, the brand says that it will be the first European model to wear the Skoda name in letters on the tailgate, rather than just as a badge, and the accompanying image shows a very similar glass tailgate lip to that of the now outgoing Rapid Spaceback. The rest of the range will follow suit with the model name spelt across the tailgate in the coming future.


Not at the moment. The plug-in hybrid version of the wafty Superb is yet to hit the market first and that arrives in the second half of 2019. Plus, the fully-electric Citigo is making its debut at the end of that year too, offering a 200km range on full charge.


Hello! Thanks for stopping by. I use this site to collect my thoughts, use as a later reference, and share with others. If you found something useful and want to get in touch, feel free to contact me.


At first glance you might think that this class only allows you to instantiate a person object but not anything more. But actually, once instantiated, you can set and get the properties by doing the following:


On June 2, which is National First Ladies Day, a book for readers 9 through 12 will be available. Entitled, LADIES, FIRST: COMMON THREADS, the book celebrates first ladies who, at one point in their lives, knitted, crocheted, embroidered, quilted, cross-stitched, or sewed. In 140 pages this unique look at 18 first ladies, from Martha Washington to Abigail Adams to Ida McKinley to Edith Wilson to Barbara Bush, will allow readers to touch history with a museum-like experience.


Each inspiring story gives a glimpse into the minds and hearts of these historic women and is threaded together by pictures of needlework and other fascinating images and photos. The book also includes places to travel in the United States or virtually to learn more about the first ladies and their important place in history.


Let's try our first program, gui1.scala:import scala.swing._class UI extends MainFrame title = "GUI Program #1" preferredSize = new Dimension(320, 240) contents = new Label("Here is the contents!")object GuiProgramOne def main(args: Array[String]) val ui = new UI ui.visible = true println("End of main function") When you compile and run the program like this:> fsc gui1.scala > scala GuiProgramOneEnd of main functionyou should see a window appearing like this:


Note: At first Reflection API looks more familiar, and it is useful, but part of learning Scala 3 macro is learning to use less of it, and use better syntactic facility, like plain quoting and matching on quotes, which we will cover later.


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