scala – function call – recursion tail

November 10, 2016November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala recursion tail

What is recursion tail in scala?

‘Recursion’ is a function that calls itself. A function that calls itself, for example, a function ‘A’ calls function ‘B’, which calls the function ‘C’. It is a technique used frequently in functional programming.

In order for a tail recursive, the call back to the function must be the last function to be performed.

scala – difference between class object

November 10, 2016November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala class object

Mention the difference between an object and a class ?

A class is a definition for a description. It defines a type in terms of methods and composition of other types. A class is a blueprint of the object. While, an object is a singleton, an instance of a class which is unique.

scala – variables vals

November 10, 2016November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala variables vals

What are the Scala variables?

Values and variables are two shapes that come in Scala. A value variable is constant and cannot be changed once assigned. It is immutable, while a regular variable, on the other hand, is mutable, and you can change the value.

The two types of variables are

var myVar : Int=0;

val myVal: Int=1;

scala – better language

November 10, 2016November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala better language

In what ways Scala is better than other programming language?

a) The arrays uses regular generics, while in other language, generics are bolted on as an afterthought and are completely separate but have overlapping behaviours with arrays.

b) Scala has immutable “val” as a first class language feature. The “val” of scala is similar to Java final variables. Contents may mutate but top reference is immutable.

c) Scala lets ‘if blocks’, ‘for-yield loops’, and ‘code’ in braces to return a value. It is more preferable, and eliminates the need for a separate ternary operator.

d) Singleton has singleton objects rather than C++/Java/ C# classic static. It is a cleaner solution

e) Persistent immutable collections are the default and built into the standard library.

f) It has native tuples and a concise code

g) It has no boiler plate code

scala – advantage

November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala lang advantage

What is the advantage of Scala?

a) Less error prone functional style

b) High maintainability and productivity

c) High scalability

d) High testability

e) Provides features of concurrent programming

scala – map

November 10, 2016November 14, 2016 corerootz - Ravi Kiran Krovvidi Scala scala Map

What is a ‘Scala map’?

Scala map is a collection of key or value pairs. Based on its key any value can be retrieved. Values are not unique but keys are unique in the Map.

scala – set

November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala Set

What is a ‘Scala set’? What are methods through which operation sets are expressed?

Scala set is a collection of pairwise elements of the same type.

Scala set does not contain any duplicate elements.

There are two kinds of sets, mutable and immutable.

scala – wild card pattern

November 10, 2016November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala wildcard pattern

The wildcard pattern (_) matches any object whatsoever. You have already seen it used as a default, catch-all alternative, like this:
expr match {

case BinOp(op, left, right) => println(expr +” is a binary operation”)

case _ => }

scala – pattern variable – start with lower case – all others constants

November 10, 2016November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala - pattern variable

Variable or constant? Constant patterns can have symbolic names. You saw this already when we used Nil as a pattern. Here is a related example, where a pattern match involves the constants E (2.71828…) and Pi (3.14159…):
scala> import math.{E, Pi} import math.{E, Pi} scala> E match { case Pi => “strange math? Pi = “+ Pi case _ => “OK” }

res11: java.lang.String = OK
As expected, E does not match Pi, so the “strange math” case is not used. How does the Scala compiler know that Pi is a constant imported from scala.math,andnotavariablethatstandsfortheselectorvalueitself? Scala uses a simple lexical rule for disambiguation: a simple name starting with a lowercase letter is taken to be a pattern variable; all other references are taken to be constants.

scala – variable pattern

November 10, 2016November 10, 2016 corerootz - Ravi Kiran Krovvidi Scala scala variable pattern

Variablepatterns A variable pattern matches any object, just like a wildcard. Unlike a wildcard, Scala binds the variable to whatever the object is. You can then use this variable to act on the object further. For example, Listing 15.6 shows a pattern match that has a special case for zero, and a default case for all other values. The default case uses a variable pattern so that it has a name for the value, no matter what it is.

expr match { case 0 => “zero” case somethingElse => “not zero: “+ somethingElse }