Partial Functions in Scala

Introduction: When a function is not able to produce a return for every single variable input data given to it then that function is termed as Partial function. It can determine an output for a subset of some practicable inputs only. It can only be applied partially to the stated inputs. Some important points:

• Partial functions are beneficent in understanding many inconsistent kind of Scala functions.
• It can be interpreted by utilizing case statements.
• It is a Trait, which needs two methods namely isDefinedAt and apply to be implemented.

Example: Here, two methods are defined for applying Partial function, where isDefinedAt states the condition and apply performs the operation if the given condition is satisfied. Methods to define Partial functions: There are some methods to define Partial function, which includes case statements, collect method, andThen, and orElse.

• Partial function using Case statement: we will create a Partial function below using case statement. Example:
  Output:

  9
  

  Here, Partial function is created using case statement so, apply and isDefinedAt is not required here.
• Partial function using orElse: This method is helpful in chaining Partial functions together. Example:
  Output:

  25
  8
  

  Here, orElse will return output for which the given condition is satisfied.
• Partial function using Collect method: Collect method requests Partial function to every single element of the collection and thus, helps in constructing a new collection. Example:
  Output:

  List(35, 45)
  

  Here, Collect will apply Partial function to all the elements of the List and will return a new List on the basis of the conditions stated.
• Partial function using andThen: This method appends at the end of the chains, which is utilized to continue towards additional chains of Partial functions. Example:
  Output:

  280
  

  Here, andThen will append the output of Partial function with the another function given and then will return that value.