Object-Oriented Programming

Free-Function Stereotypes

Michael L. Collard, Ph.D.

Department of Computer Science, The University of Akron

UML Stereotypes

Code Stereotype

  • A label we give to code to distinguish it further
  • Will look into method stereotypes and class stereotypes later in the course
  • Here, we will look at stereotypes from the perspective of free functions

Why Categorize into Stereotypes?

  • Functions are a general language feature that is used for many different purposes
  • Functions of a particular stereotype share many characteristics and are more similar
  • Make sure we have explored the full range of what we can use
  • Shorthand for documentation

Free Function Stereotypes

  • Accessor::property
  • Accessor::predicate
  • Mutator::command


  • Executes a change based on the IN/OUT parameters
  • For data the function changes, parameters are IN/OUT or OUT
  • These parameters are pass by reference (not pass by const reference)
  • Other parameters may be IN


  • Returns information derived from the IN parameters
  • Parameters are pass by value or pass by const reference
  • When iterators are used, pass by value of const_iterator


  • Returns a Boolean result derived from the IN parameter
  • Parameters are all IN
  • Must pass all data directly used in the condition
  • Useful for even short conditions as it gives them a name
  • Often used in refactorings


  • Often extracted from code with complex conditional statements
  • Anywhere to hide details on how the predicate is determined

Accessor::predicate naming

  • Set of standard terms that everyone knows means a predicate
  • If not a standard term, then verb form often starts with is
  • Other verb forms depending on the context
  • Do not include the parameter or return types in the name, e.g., no "bool"
  • Never use the term "returns" in a function name