title: Purely functional
text: # Purely functional
  
  Purely functional may refer to:
  
  ## Computer science
  
  * Pure function, a function that does not have side effects
  * Purely functional data structure, a persistent data structure that does not rely on mutable state
  * Purely functional programming, a programming paradigm that does not rely on mutable state
  
  ## Law
  
  * Functionality doctrine, in intellectual property law
  