Oliver Sturm

• Training Director at DevExpress

• Consultant, trainer, author, software architect and developer for 30 years

• Contact: oliver@oliversturm.com

Agenda

• Basics - so we're on the same page
• Several real use cases from FCSlib
• Be like Haskell

Pattern Matching - C# Versions

• C# 7: value is Type t, also in switch
• C# 8: switch expressions, property, tuple, positional patterns, deconstruction
• C# 9: logical (and, or, not), relational (operators) and structural (parens) enhancements
• C# 10: nested property patterns
• Future, potentially: list patterns (e.g. is [1,2,3])

FCSlib examples

• Construct a tuple as needed to match with a positional pattern
• Replace ternary expressions?
• Combine matching methods (property and type patterns) to cover different cases efficiently
• Relational pattern to deal with Comparer<T>

Be like Haskell

data Color = R | B
data RedBlackSet a = E | T Color (RedBlackSet a) a (RedBlackSet a)
balance B (T R (T R a x b) y c) z d = T R (T B a x b) y (T B c z d)
balance B (T R a x (T R b y c)) z d = T R (T B a x b) y (T B c z d)
balance B a x (T R (T R b y c) z d) = T R (T B a x b) y (T B c z d)
balance B a x (T R b y (T R c z d)) = T R (T B a x b) y (T B c z d)
balance color a x b = T color a x b

Sources

• This presentation:
  https://oliversturm.github.io/advanced-pattern-matching-cs
• PDF download:
  https://oliversturm.github.io/advanced-pattern-matching-cs/slides.pdf
• Repository with sample code:
  https://github.com/oliversturm/advanced-pattern-matching-cs-samples
• FCSlib: https://github.com/oliversturm/FCSlib