Functional Programming in C#
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Functional programming in C# emphasizes: 1) Using data objects instead of primitive types for more specific arguments and results. 2) Writing "honest functions" that always return an expected output given valid inputs without exceptions. 3) Composing values using tuples to aggregate data objects. 4) Avoiding null values with Option<T>. 5) Applying LINQ queries instead of foreach loops.
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Functional Programming in C#
- 1. Functional programming in C# Tadeusz Balcer
- 2. DISCLAIMER
- 3. DISCLAIMER I’M NOT AN EXPERT IN THIS TOPIC!
- 4. DISCLAIMER I’M NOT AN EXPERT IN THIS TOPIC! But I will try to show you what I have learnt
- 5. Agenda 1. Introduction a) What is functional programming? b) Separation between functions and arguments (data) c) Benefits of Functional Programming 2. Functional programming in C# a) Data Objects b) Honest functions c) Tuple and ValueTuple d) Option<T> e) LINQ
- 6. What is Functional Programming?
- 7. What is Functional Programming? • Functional programming is a paradigm which concentrates on computing results rather than on performing actions.
- 8. What is Functional Programming? • Functional programming is a paradigm which concentrates on computing results rather than on performing actions. • Functional programming is programming with mathematical functions - used functions should always provide the same results for the same input.
- 9. What is Functional Programming? • Functional programming is a paradigm which concentrates on computing results rather than on performing actions. • Functional programming is programming with mathematical functions - used functions should always provide the same results for the same input. • At very high level, it's a programming style that emphasizes functions while avoiding state mutation.
- 10. What is Functional Programming? • Functional programming is a paradigm which concentrates on computing results rather than on performing actions. • Functional programming is programming with mathematical functions - used functions should always provide the same results for the same input • At very high level, it's a programming style that emphasizes functions while avoiding state mutation. • Functional programming is a style that treads computation as the evaluation of mathematical functions and avoids changing-state and mutable data
- 11. Separation between functions and arguments (data) • In Object Oriented Programming, state (data) and methods (functions) are bounded in objects
- 12. Separation between functions and arguments (data) • In Object Oriented Programming, state (data) and methods (functions) are bounded in objects • In functional programming, logic is encoded in functions and data is captured with data objects, which are the input and output of functions
- 13. Separation between functions and arguments (data) • In Object Oriented Programming, state (data) and methods (functions) are bounded in objects • In functional programming, logic is encoded in functions and data is captured with data objects, which are the input and output of functions • Math functions are not class method. Math functions does not leave any mark of it's exsistsence in outside world, while class methods may change the state of an object.
- 14. Functions
- 15. Methods
- 16. Functional programming in practice
- 18. Benefits of Functional Programming • Tamed Side Effects • Simple concurrency (no shared variables) • Straightforward unit testing • Different point of view for looking at problems
- 19. Benefits of Functional Programming
- 20. Benefits of Functional Programming
- 25. Use more specyfic arguments and results Data Objects instead of Primitive Types
- 26. Why use more specyfic data types? • Primitive types are often not specific enough - for example, if you take age, int can be -1000 as well as 1000.
- 27. Why use more specyfic data types? • Primitive types are often not specific enough - for example, if you take age, int can be -1000 as well as 1000. • You’ll have to write additional unit tests for the cases in which validation fails.
- 28. Why use more specyfic data types? • Primitive types are often not specific enough - for example, if you take age, int can be -1000 as well as 1000. • You’ll have to write additional unit tests for the cases in which validation fails. • There are a few other areas of the application where an age is expected, so you’re probably going to need the same validation in those places. This will cause duplication.
- 29. Data Objects
- 32. Data Objects – interaction with primitive types
- 33. Data Objects – interaction with primitive types
- 34. Data Objects – implicit/explicit operators
- 35. Data Objects – implicite/explicit operators
- 36. Honest functions
- 37. Honest functions • Honest function - it always honors signature. There is no other possible outcome than defined (also no error throw). It just maps each element of domain to an element of the codomain. Function is honest if ts behavior can be predicted by its signature. No throwing exceptions, and no null return values.
- 38. Honest functions • Honest function - it always honors signature. There is no other possible outcome than defined (also no error throw). It just maps each element of domain to an element of the codomain. Function is honest if ts behavior can be predicted by its signature. No throwing exceptions, and no null return values. • Dishonest function - give ma an int, and I may return a Risk.
- 39. Honest functions
- 41. Honest functions
- 42. Honest functions
- 43. Honest functions
- 44. Honest functions DISHONEST SIGNATURE HONEST SIGNATURE
- 45. Composing values
- 46. Composing values with tuples
- 47. Tuple
- 48. TupleValue
- 49. Avoiding nulls
- 51. Avoiding null bomb – Option<T>
- 52. Avoiding null bomb – Option<T>
- 54. Avoiding null bomb – Option<T>
- 55. Avoiding null bomb – Option<T>
- 56. LINQ
- 59. LINQ
- 63. Summary • Data Objects instead of Primitive Types • Honest functions to have output for every possible input • ValueTuple to aggregate Data Objects • Option<T> to avoid nulls • LINQ instead of foreach
- 65. Bibliography • Functional Programming in C#: How to write better C# code (2017)
- 66. Bibliography (Pluralsight) • Functional Programming with C# (Dave Fencher) (2015) • Applying Functional Principles in C# (Vladimir Khorikov) (2016) • Making Your C# Code More Functional (Zoran Horvat) (2018)
- 67. Bibliography (Presentations) • Railway oriented programming: Error handling in functional languages by Scott Wlaschin (link) (2014) • Functional Programming in C# (link) (2018)
- 68. Questions?
- 69. Thank you!