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Scala Constructs
In this tutorial, we will learn about constructs with examples in Scala.
Submitted by Shivang Yadav, on February 02, 2021
Constructs in Scala
Constructs in a programming language are the building blocks or basic programming concepts that are defined in it.
Types of Scala Constructs
In Scala Programming Language, the constructs defined are,
- Expression
- Values and variables
- Functions
- Methods
- Blocks
- Classes and objects
- Traits
- Fields
- Closures
- Main method
Let's discuss these in detail,
1) Expressions
A line of code that can be compiled and has some resultant value is expression. These are displayed on screen using println statements.
Example
A * B
"String"
Program to illustrate expressions in Scala
object MyClass {
def main(args: Array[String]) {
println(45 * 24332);
println("Scala programming Language!")
println("My Score is " + (456.0*100.0/500.0) + "%")
}
}
Output
1094940
Scala programming Language!
My Score is 91.2%
In the above code, we have illustrated the use of expression in Scala. Using the println statement, we have printed different expressions. Like, mathematical expression, string and concatenated values.
2) Values and Variables
In Scala values can be stored in order to use the resulting value of expression later or it another expression.
Scala program two type to store values,
(a) Values
These are constant holders to hold the result of an expression. You can store the result of an expression in value which is initialized as val. But you cannot change the value stored once.
Syntax
val value_name = "Value to be stored"
Program to illustrate the working of vals in Scala
object MyClass {
def main(args: Array[String]) {
val a = 45 * 24332
println(a)
val result = (456.0*100.0/500.0)
println("My Score is " + result + "%")
}
}
Output
1094940
My Score is 91.2%
In the above code, we have stored expression values in a variable using val initialization. You can see that though we have not used the variable more than once, we could not reuse it to store the value of the second expression as it is initialized as val which is not reusable.
(b) Variables
These are holders that store the results of an expression. They are declared using val keywords. The plus point in working with val declarations is that you can re-initialize the values in val i.e. you can re-assign the variable with another value.
Syntax
Creating a variable,
var variable_Name = "expression"
Reassigning value,
variable_Name = "another_expression"
Program to illustrator the working of variables
object MyClass {
def main(args: Array[String]) {
var value = 45 * 24332.0
println(value)
value = (456.0*100.0/500.0)
println("My Score is " + value + "%")
}
}
Output
1094940.0
My Score is 91.2%
In the above code, we have used a var declaration to store the expression result and then we have re-initialized it to store another result. This is possible if we are using val declaration. But the type of both the expressions should be the same.
Some important point on variable in Scala:
3) Function
A function is a reusable chunk of code that can perform the operation on the value passed as a parameter.
Anonymous functions are special functions that are assigned to a variable.
Syntax
Function
(parameter: Type ) => return_Expression
Anonymous Function:
val variable_Name = (parameter: Type ) => return_Expression
Calling a function:
variable_Name(valueToBePassed)
Example
val result = (mark: Float ) => mark*100/500
Program to illustrate the working of functions in Scala
object MyClass {
def main(args: Array[String]) {
var result = (marks: Double ) => marks*100 / 500
println("My Score is " + result(462.4) + "%")
}
}
Output
My Score is 92.48%
Some important concepts on functions in Scala
4) Methods
A method is a block of code that can perform a certain amount of tasks. It is similar to a function. It is defined using the def keyword. It has a parameter list to accept values of performing operation on and the resultant value is also returned.
Syntax
def methodName (parameters) : (return Type) = {
// statements to be executed…
}
Program to illustrate the working of methods
object MyClass {
def calcResult(marks : Double) : (Double) = {
return marks*100 / 500
}
def main(args: Array[String]) {
println("My Score is " + calcResult(462.4) + "%")
}
}
Output
My Score is 92.48%
Some important concepts on method in Scala
5) Block
A block is referred to as multiple statements that are enclosed between curly braces.
Syntax
{
// statement 1
// statement 2
...
}
Program to illustrate the working of block in Scala
object MyClass {
def main(args: Array[String]) {
{ // this is a block in scala
val marks = 315.12
val score = marks*100 / 500
println("My Score is " + score + "%")
}
}
}
Output
My Score is 63.024%
6) Classes and Objects
A class is a blueprint for objects. It contains the definition of all the members of the class. There are two types of members of the class in Scala,
Fields: the variables in Scala that are used to define data in the class.
Methods: The functions of a class that are used to manipulate the fields of the class and do some stuff related to the functioning of a class.
You can read more on classes here…
7) Traits
Traits in Scala are like interfaces in Java. A trait can have fields and methods as members, these members can be abstract and non-abstract while creation of trait.
More on traits...
8) Closure
Closures use one or more values that are not declared in the function to give the final output.