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EECS 280 Lab 10: Functors

Lab Due Thursday, July 4, 2024, 11:59 pm

In this lab, we will practice defining and using functors, which are similar to function pointers, but much more powerful. They behave just like any other object in your program and maintain a state, but they can act like a function because we overload the function call operator.

Completion Criteria/Checklist:

To pass this lab, you must finish tasks 1 and 2. Task 1 focuses on comparators while task 2 focuses on predicates, both of which are functors.

• Finish the CompareName and CompareAge functors.

• Complete the IsAgeN predicate functor.

• Add code to print_if.

• Add code to print_people_with_age_n and use IsAgeN and print_if.

Lab Exercises

The Files

Here's a summary of this lab's files.

File	Description
lab10.h	Contains the Person class and some simple functors and functions for convenience.
lab10.cpp	Contains functor and function definitions.
main.cpp	Contains the main function that runs testing code.

Testing Code

The main function in main.cpp contains some testing code we've written for you, which will print the results produced by your code.

The starter code should compile successfully without any modifications, so make sure you are able to compile and run it with the following commands. The code may be missing some pieces, contain some bugs, or crash when you run it, but you'll fix each throughout the course of the lab.

$ g++ -Wall -Werror -g -pedantic --std=c++17 lab10.cpp main.cpp -o lab10.exe
$ ./lab10.exe

Introduction

The Person class

Throughout this lab we will be working with a Person class. Make sure to check lab10.h to get familiar with its public interface.

Task 1 - From Functions to Functors

Your first task will be working with comparators, functors that compare two objects.

You must finish the two functors CompareName and CompareAge, which let us compare two Persons' names and ages respectively.

Take a look at the find_max function. Here you can see a comparator being used to compare two persons in order to find the max person in an array.

Note that by overriding operator() our comparator objects can be invoked like a function.

Task 2 - Functors with Internal State

Your second task will now focus on predicates, a functor that returns true or false based on some statement.

To begin, finish the functor IsAgeN, which lets us check if a Person has a specific age. In order to accomplish this, the functor will need to have a custom constructor to specify what age it should check for and a private member variable to keep track of that age.

Next, complete print_if which uses a predicate to determine which parts of an array should be printed.

Finally, you will need to write print_people_with_age_n to print all the people of age n. You should do this by using the functor IsAgeN and the function print_if you just wrote.