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F# Interview Questions

A list of top frequently asked F# interview questions and answers are given below.

1) What is F#?

F# is a Computer programming language. It was designed and developed by Microsoft. It supports functional, object-oriented and imperative programming approaches. You can create any type of application by using this programming language.

2) What are the features of F#?

F# has many features. Following are the main features of F#:

  • Type inference
  • Type extension
  • Less code
  • Immutable data
  • Pattern matching
  • Assertion
  • Lambda expression
  • Function composition and pipelining
  • Object expression
  • Lazy computation and many more

3) What are available data types in F#?

F# provides rich set of data types. It helps to deal with any type of data whether it is scientific data, data of business analysis etc. You can see table of data types here.

4) What is unit type in F#?

The unit type is a type which indicates the absence of specific value. The unit type has only a single value. This value acts as a placeholder when no other value exist.

5) What is upcasting and downcasting in F#?

Casting is a process of converting one type to another type. F# provides mainly two operators to deal with upcasting and downcasting. Further details are available here.

6) What are available operators in F#?

An operator is simply a symbol that is used to perform operations. There can be many types of operations like arithmetic, bitwise, logical etc.

There are following types of operators to perform different types of operations in F# language.

  • Arithmetic operators
  • Boolean operators
  • Bitwise operators
  • Nullable operators

7) What is function composition and pipelining in F#?

In F#, functions can be composed from other functions. It is a process of composing in which a function represents the application of two composed functions. F# function pipelining allows us to call functions in chain. Pipelining operator takes a function and an argument as operands and returns a value.

8) What is lambda expression in F#?

Lambda expression is an unnamed or anonymous function. Sometimes instead of defining a full name function you may create a lambda expression. It optimizes the code. You must use fun keyword to define lambda expression.

9) What is inline function in F#?

F# inline function is a function that is integrated directly into the calling code. It helps to optimize code and sometimes can improve performance too.

10) What is let bindings in F#?

Binding is a process of associating of identifier or function to a value. Let keyword is used to bind identifier to a value. In F#, We use let keyword to declare variable, function and private class members.

11) What is do bindings in F#?

Do binding is used to execute code without defining function or any type. You can write independent code by using do binding in F#.

12) What is type annotation in F#?

F# allows type annotation so that you can explicitly mention the type of identifier or parameter or return type of a function. You must use: (colon) to apply annotation in F#.

13) What is Type Inference in F#?

Type inference means when you are writing code then you don't need to specify type of values or variables. F# compiler is strong enough to infer the type of value.

14) What is Automatic Generalization in F#?

When code does not specify any type explicitly then the compiler considers generic type. This is called automatic generalization. It helps to write generic code without increasing complexity.

15) What is Tuples in F#?

In F#, tuples are collection of anonymous values. Values may be same or different types. It allows us to put expression as a value also.

16) Can a function return multiple values in F#?

Yes, by using tuple, you can return multiple values in a function. See an example.

17) What is list in F#?

It is immutable collection of same type elements. It maintains order of elements.

18) What is Array in F#?

Arrays are mutable collections of data of same type. It starts from 0 index and goes to n-1 where n is length of arrays.

19) What is Sequence in F#?

Sequence is a series of same type of elements. It provides better performance than list.

20) What is options in F#?

Options type is used when there is no value present for function or variable. It provides an expression Some and a value None for handling the empty values or variables.

21) What is Generics in F#?

F# allows you to write generic function, method, type, variable etc. It helps to avoid repeating of code for each type. By writing generic code you can apply it for any type or value.

22) What is Records in F#?

Records are used to store elements in the form of label and value. It can store any type of data. You are not bound to store same type values as list. Records are immutable by default so you can't modify original records.

23) What is Enumeration in F#?

Enumeration is popularly known as enums. It is a combination of label and value pair. Labels are assigned to a subset of the values. You can use them in place of literals to make code more readable and maintainable.

24) What are Reference cells in F#?

Reference cells refer to memory locations. It allows you to create mutable values. F# uses immutable data structure by default.

25) What is structure in F#?

F# structure is a data structure which is used to organize data, it is value types and efficient than class. It does not allow let binding, so you must declare fields by using val keyword.

26) What is Discriminated Union in F#?

It is useful data structure. It helps to store heterogeneous data. Union is used to represent tree data structures. It provides cases and each case consist of heterogeneous data.

27) What is Object in F#?

Object is a real world entity. It can be anything like - cell phone, car, football etc.

Object is an instance of class we can access all the members of class by using object of this class.

28) What is class in F#?

Class is a template or blue print of an object. It is used to encapsulate data members and member methods. It can contain fields, methods, constructor, static method etc.

29) What is constructor in F#?

In F#, Constructor is somewhat different than other .Net languages. There are always primary constructors that may or may not have parameters. Scope of these parameters is throughout the class.

30) What is self in F#?

In F#, self is used to refer current object of class type. Self is same as this keyword in C# and java. You can name the self identifier however you want. You are not restricted to names such as this or self as in .Net languages.

31) What is static in F#?

In F#, static is a keyword. It is used to make static field or static method. Static is not the part of object. It has its own memory space to store static data. It is used to share common properties among objects.

32) What is inheritance in F#?

In F#, inheritance is a process in which child class acquires all the properties and behaviors of its parent class automatically. It is used to reuse the code.

33) What is method overriding in F#?

Method overriding is a feature of Object oriented programming approach. It helps to achieve polymorphism. We can achieve method overriding using inheritance.

34) What is abstract class?

Abstract classes are those which don't provide full implementation of class members. It may contain non abstract methods. A class that inherits abstract class must provide implementation of all abstract methods of abstract class.

35) What is interface in F#?

F# provides Interface type. It provides pure abstraction. It is a collection of abstract methods.

36) What is type extension in F#?

Type extension allows you to add new members to your previously defined object type.

37) What is delegate in F#?

In F#, delegates are reference types. It allows us to call function as an object. It is a feature of this language. It gives advantage over the other functional programming languages.

38) What is objects expression in F#?

F# objects expression is a special expression. It creates a new instance of anonymous object type which is based on an existing base type, interface, or set of interfaces.

39) What is Exception handling?

Exception handling is a standard mechanism to handle abnormal termination of program. Exception is a situation that occurs during program execution. It may lead to terminate program abnormally like dividebyzero or nullpointer.

40) What is try-with block in F#?

In F#, you can create user defined exception. It provides flexibility to define custom exceptions according to requirement.

41) What is FailWith and InvalidArg in F#?

In F#, you can throw exceptions explicitly. You are allowed to throw custom exception. You can also throw exceptions by using predefined methods of Exception like Failwith and InvalidArgs.

42) What is assertion in F#?

The assert expression is a debugging feature of F#. You can use it to test an expression. It generates a system error dialog box upon failure in Debug mode.

43) What is module in F#?

Module is a collection of classes, functions, and types. It helps to organize related code so we can maintain code easily.

44) What is access control in F#?

Access control specifies the accessibility of code. By using these you can specify the scope of data, method, class etc.

There are 3 types of access control in F#.

  1. Public or Default
  2. Private
  3. Internal

45) What is Resource management in F#?

F# manages resources with the help of use and using keywords. Resources may be data, a file or network etc. It acquires resource from operating system or other service provider so that it can be provided to other application.

46) What are attributes in F#?

In F#, attribute is used to enable metadata for program code construct. Attribute can be applied to any construct like function, module, method and type.

47) What is signature in F#?

In F#, signature file contains information about the public signatures. Signatures can be of a set of program elements, such as types, namespaces, and modules.

48) What is open keyword in F#?

An import declaration specifies a module or namespace. You can reference it's elements without using a fully qualified name.

49) What is lazy computation in F#?

Lazy computation is a feature of F#. Lazy computation does not evaluate immediately. It is executed when result is needed.

50) What is XML documentation in F#?

In F#, you can produce documentation from triple-slash (///) code comments. XML comments can precede declarations in code files (.fs) or signature (.fsi) files.