programming in scala

Scala is famous recently, but it is really so good. What I see is nothing. Scala's fame masks its shortcomings, so many people do not see its shortcomings. Although it is a functional programming language, it gives me the overall feeling of confusion and inconsistency, to be different, do you have to be different from other languages to show your excellence? You know, Java has been tested for more than 20 years. Isn't it worth learning from? Are you s

We talked about getting started with Scala, but after all, it's not like scripting language, and Scala is talking about replacing Java, so we'll see how he grabs the Java position.A common editor for Scala, see below: Eclipse (using one of the shoddy and unstable Scala plugins) Emacs IntelliJ (basicall

Scala: Operator and parser, scala operator ParsingThe names of variables, functions, and classes are collectively referred to as identifiers. The backquotes can contain almost any character sequence.In scala,-Operator ending with Colon-Value assignment operatorAll operators are left-bound. The unapply method accepts an object and then takes the value from it, us

The trait definition in Scala includes a collection of fields, behaviors (methods/functions/actions), and some non-implemented functional interfaces that can be easily extended or mixed into existing classes or abstract classes.Scala's trait (trait) is a very useful feature that can be better abstracted in the design. The program is more extensible by making programs more focused on their features and better splitting the program into multiple trait m

In this Martin and two other pattern matching experts ' papers, there are several ways to implement pattern matching, and Scala chooses which way to implement it.Http://lampwww.epfl.ch/~emir/written/MatchingObjectsWithPatterns-TR.pdfI quoted some of the descriptions inside.In object-oriented programs, data is organized into class-level classesThe problem with object-oriented language in pattern matching is how to detect this level from the outside.The

The main contents of this article are as follows: Variables and invariants Functions and procedures Parameters of the function Semicolon 1. Variables and invariants 1.1. VariablesScala's variables are divided into two types, Var and val. var, or variable, is similar to the variables we touch in other languages such as Java, and Val, is value, similar to the non-assignable constants we use in other languages, or the final variable.Why this difference, this is because in

Scala briefly -- class and object, scalaClass In scala, classes are not declared as public. The source file can contain multiple classes, all of which have common visibility. The getter and setter methods are provided for each field, which are called Field Names and field name_, respectively, and can be customized. Note: 1) if the field is private, getter and setter are also private. 2) if the field is val

Let's look at a loop in Java: for (int i = 1; i ) { + ",");}There is no doubt that Scala can make this loop more concise. According to the previous section, it is not necessary to display the type of the specified variable i, and we do not even need to declare the variable. The next output statement can be more concise, and in Scala you can use the println () method to output a string directly. Finall

Package Com.leegh.parameterizationImport Com.leegh.parameterization.Compound_Type/*** @author Guohui Li*/Trait Compound_type1;Trait Compound_type2;Class Compound_type extends Compound_type1 with compound_type2Object Compound_type {def compound_type (x:compound_type1 with compound_type2) = {println ("Compound Type in Global Method")}def main (args:array[string]): Unit = {Compound_type (new compound_type1 with Compound_type2)Object Compound_type_object extends Compound_type1 with compound_type2Com

Package Com.leegh.parameterization/*** @author Guohui Li*/Class Pair_ordering[t:ordering] (Val first:t, Val second:t) {def bigger (implicit ordered:ordering[t]) = {if (Ordered.compare (first, second) > 0) First Else second}}Object Context_bounds {def main (args:array[string]): Unit = {Val pair = new pair_ordering ("Spark", "Hadoop")println (Pair.bigger)Val pairint = new Pair_ordering (3, 5)println (Pairint.bigger)}}Report:This blog description:1. Organize your ideas and improve yourself.2. Be ed

We do spark development using a lot of spark's higher-order functions so today I'm using scala higher-order functions on Linux ServicesDeclares a list collection:The package containing the list is already automatically introduced by the predefined, so there is no need to introduce a package here, directly using the list instantiation object, actually using the list object object's Apply methodWe use the map function to multiply each value in the list

Question: Convert the text string "[1, 2, 3, 4, 5]" to an array. Answer:val x = "[1, 2, 3, 4, 5]"Val y =x Slice (1, x.length-1) replace (",", "") Split ("")var y1= x Slice (1, x.length-1) replace (",", "") Split ("") Map (_.toint)Y1:array[int] = Array (1, 2, 3, 4, 5)or writevar y1= x.slice (1, x.length-1). Replace (",", ""). Split (""). Map (_.toint)OrVal y:array[int]= x Slice (1, x.length-1) replace (",", "") Split ("") Map (_.toint)Scala encourages

001-scala development environment Construction and HelloWorld parsingScala functional programming and object-oriented language functional programming excel at numerical computing object-oriented organization of large-scale engineering and project and team collaboration Scala will be the next great language? Spark is written in the Scala language, and Hadoop is wr

Scala: annotation and scala AnnotationAnnotations can be used to add information to various entries of a program. They are inserted into the code so that tools can process tags for them. You can use java annotations for scala classes or scala-specific annotations.In scala, a

Java programmers, why do you need to pay attention to Scala, Java programmers, and Scala? Let's take a look at Martin Odersky's design goals for Scala. What aspects should be taken into account in the process of creating a language that surpasses Java? Concession Frank Sommers: You mentioned earlier that you want to create a language that exists in the Java

Package Com.leegh.parameterization/*** @author Guohui Li*/Import Scala.reflect.ClassTagClass Trible[f, S, T] (Val first:f, Val second:s, Val third:t)Object Hello_type_parameterization {def main (args:array[string]): Unit = {val triple = new Triple ("Spark", 3, 3.1415)Val bigdata = new triple[string, String, Char] ("Spark", "Hadoop", ' R ')def Getdata[t] (list:list[t]) = List (LIST.LENGTH/2)println (GetData (List ("Spark", "Hadoop", ' R '))Val F = getdata[int]_println (f (List (1,2,3,4,5,6,7,8)))

Github:https://github.com/nscala-time/nscala-timeMAVEN: (Pay attention to the Scala version)Dependency> groupId>Com.github.nscala-timegroupId> Artifactid>nscala-time_2.10Artifactid> version>2.6.0version>Dependency>code example:Remember import com.github.nscala_time.time.imports._ scala> DateTime.Parse ("20150101", DateTimeFormat forpattern ("YyyyMMdd"))Res11:org.joda.time.DateTime = 2015-01-01t00:0

Package Com.leegh.implicits/*** @author Guohui Li*/Object Context_implicits {Implicit val default:string = "Java"}Object Param {def print (content:string) (implicit language:string) {println (language + ":" + content)}}Object Context_parameters {def main (args:array[string]): Unit = {Param.print ("Spark") ("Scala")Import Context_implicits._Param.print ("Hadoop")}}Report:This blog description:1. Organize your ideas and improve yourself.2. Be educated i

We know that everything in Scala is an object, a function is an object, a number is an object, and it's a more object-oriented language than Java.Simple classes that define ScalaClass Point(val x:int, val y:int) The previous line of code is the definition of a Scala class: The first is the keyword class followed by the class name point The parentheses after the class name are the const

Package Com.leegh.parameterization/*** @author Guohui Li*/Because breathe returns This,scala the return type is inferred as animal, and because animal has no eat methodClass Animal {def breathe = this}Class Cat extends Animal {def eat = this}Class Animal {def Breathe:this.type = this}Class Cat extends Animal {def eat:this.type = this}Object Singleton_types {def main (args:array[string]): Unit = {Val cat = new CatCat.breathe.eat}}Report:This blog descr