function parameter

How to define Scala methods that take complex functions as parameters (syntax)

Problem: You want to define a Scala method that takes a function as a parameter, and that function may have one or more input parameters, and may also return a value.

Solution: Following the approach described in the previous recipe, define a method that takes a function as a parameter. Specify the function signature you expect to receive, and then execute that function inside the body of the method.

Scala: How to define a generic method parameter that must extend a base type

In today’s installation of “how to have fun with Scala,” if you want to define a method that takes a parameter that has a generic type, and want to further declare that the parameter must extend some base type, use this syntax:

def getName[A <: RequiredBaseType](a: A) = ???

That example says, “The parameter a has the generic type A, and A must be a subtype of RequiredBaseType.”

This is a page from my book, Functional Programming, Simplified

How to Write Scala Functions That Take Functions as Input Parameters

“Haskell functions can take functions as parameters and return functions as return values. A function that does either of those is called a higher order function. Higher order functions aren’t just a part of the Haskell experience, they pretty much are the Haskell experience.”

From Learn You a Haskell for Great Good

How to define a Scala method that accepts a function parameter

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 9.3, “How to define a method that accepts a simple function parameter.”

Problem

You want to create a method that takes a simple function as a method parameter.

Solution

This solution follows a three-step process:

A simple Scala call-by-name example

Here’s a simple Scala call-by-name example. I’ll show the normal approach to writing a method and passing in a parameter, and then show a call-by-name (pass by name) example.

1) A “normal” Scala method (call-by-value)

Here I show how to pass a parameter to a method “normally,” i.e., call by value: