First-Class Functions in Practice Quiz Quiz

Explore key principles of first-class functions with this quiz, designed to reinforce understanding of using functions as values, arguments, and return types. Perfect for learners seeking to grasp practical uses and theory behind first-class function behaviors.

1. Function Assignment

   Which statement best demonstrates treating a function as a value by assigning it to a variable?

   1. Assigning the result of a function call to a variable
   2. Declaring a variable and assigning it a number
   3. Assigning a function to a variable, then calling it with the variable’s name
   4. Using a for loop to repeat a statement five times

   Explanation: Assigning a function to a variable and then calling it by that variable’s name is a core feature of first-class functions, as it treats functions as values that can be referenced and invoked. Assigning a number to a variable only involves numbers, not functions. Using a for loop does not inherently involve first-class functions. Assigning the result of a function call to a variable saves the return value, not the function itself as a value.

2. Passing Functions as Arguments

   Which of the following scenarios best illustrates using a first-class function as a callback?

   1. Declaring a function that uses global variables
   2. Passing a function as an argument to another function
   3. Calling a function directly in a global statement
   4. Returning a single integer from a function

   Explanation: Passing a function as an argument enables the receiving function to call or store it, which is a key use of first-class functions often called a callback. Returning a single integer does not utilize first-class functions. Declaring a function with global variables deals with scope, not first-class functions. Calling a function in a global statement is just normal invocation, not passing the function as a value.

3. Returning Functions

   What is the result of a function returning another function as its output?

   1. The returned value is a function that can be called later
   2. The outer function cannot have parameters
   3. The programming language will generate a syntax error
   4. The original function gets overwritten

   Explanation: Returning a function from another function allows you to later use or invoke the returned function, a core aspect of first-class function support. The original function itself remains unaffected and is not overwritten. There are no restrictions making the outer function parameterless. In languages supporting first-class functions, this construct is syntactically valid, so there is no syntax error.

4. Functions in Data Structures

   Which action directly demonstrates storing a first-class function inside a data structure, such as a list or object?

   1. Declaring several unrelated variables
   2. Writing a function that prints a message
   3. Sorting a list that contains only numbers
   4. Adding a named function as an element in a list

   Explanation: Storing a named function in a list leverages first-class functions by allowing functions to exist as data structure elements, retrievable and callable. Declaring unrelated variables does not use or store functions. Writing a function that prints a message focuses only on function definition, not storage. Sorting a list of numbers is unrelated to function storage as values.

5. Practical Application: Higher-Order Functions

   When creating a higher-order function that modifies behavior based on a parameter, which feature of first-class functions is being put into practice?

   1. Receiving functions as parameters to customize process logic
   2. Limiting function access to specific modules
   3. Using constants to store non-changing values
   4. Relying on recursive function calls for repetition

   Explanation: Allowing a function to receive other functions as parameters enables you to tailor or modify its behavior dynamically, utilizing first-class function principles. Using constants relates to values that do not change, not function behavior. Recursion is a different concept about functions calling themselves. Limiting function access speaks to encapsulation and visibility rather than first-class functions.