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HPM Education - Haskell
  • Introduction to Haskell
  • Introduction
    • Functions
    • Functional Programming vs Imperative Programming
    • Installing Haskell
    • Haskell Modules
    • Loading Modules into GHCi
    • Expressions
    • Laziness
    • Immutability
  • Types in Haskell
    • Introduction
    • Basic Types
    • Static Type Check
    • Polymorphic and Overloaded Types
    • Data Structure Types
      • Lists
        • List Functions
      • Tuples
    • Function Types
      • Curried Functions
      • Partial Application
  • Defining Functions / Working with Functions
    • The Layout Rule
    • Local Definitions
    • The Infix Operator
    • Conditionals
      • If-then-else Statements
      • MultiWayIf
      • Guarded Equations
      • Case-of Statements
    • Pattern Matching
      • Tuple Patterns
      • List Patterns
    • Lambda functions
    • Function Operators
  • List Comprehensions
    • List Comprehensions
  • Higher-order Functions
    • Introduction
    • The map Function
    • The filter Function
  • Recursion
    • Introduction
    • 4 Steps to Defining Recursive Functions
    • Recursion Practice
    • Folds
      • Fold Right (foldr)
      • Fold Left (foldl)
  • Cutom Types
    • Declaring Types
      • Type Synonyms
      • Data Declarations
      • Newtype declarations
  • Type Classes
    • Introduction
    • Basic Classes
      • Eq – Equality Types
      • Ord – ordered types
      • Show – Showable Types
      • Read – readable types
      • Num – Numeric Types
      • Integral – Integral Types
      • Fractional – Fractional Types
      • Enum – Enumeration Types
    • Derived Instances
    • Exercise – Making a Card Deck Type
  • Interactive Programming
    • Introduction
    • Input / Output Actions
    • Sequencing Actions
    • Exercise - Numbers Guessing Game
  • Functors, Applicatives and Monads
    • Introduction
    • Functors
    • Applicative Functors
    • Monads
      • Maybe Monad
      • List Monad
      • Monad Laws
  • References / Further Reading
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  1. Defining Functions / Working with Functions
  2. Pattern Matching

Tuple Patterns

We can think of a tuple pattern as a tuple of lower-level patterns – the lower-level patterns match individual elements in the tuple. That tuple of patterns itself makes a full pattern that matches any tuple with the same length and whose elements match the internal patterns. We could use tuple patterns for functions that return the suit and the rank of a playing card represented by a tuple:

getSuit :: (String, String) -> String
getSuit (suit, _) = suit

getRank :: (String, String) -> String
getRank (_, rank) = rank

ghci> getSuit ("Hearts", "Ace")
"Hearts"
ghci> getRank ("Hearts", "Ace")
"Ace"

We check that the tuple passed in is of arity two, and then return the first or second element depending on what we want to get.

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Last updated 2 years ago

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