Build a Simple Calculator

Learning Goals

• Use Ruby math operations to build a calculator
• Define instance method
• Use the Ruby Math class to call a method provided by Ruby

Introduction

Calculators can be very useful devices in day-to-day activities. You've likely used a calculator to add up bills for this month or calculate the tip at a restaurant. We're going to take our arithmetic knowledge and put it to the test by writing functions that will do basic math calculations for us, just like we can see in IRB.

Use Ruby Math Operations to Build a Calculator

Fork and clone this repo and open lib/math.rb. You'll find a bunch of empty methods that take numbers as arguments. Build the appropriate behavior for each of the following methods:

• addition - Build the method addition that adds num2 to num1 and returns the result of this calculation
• subtraction - Build the method subtraction that subtracts num2 from num1 and returns the result of this calculation
• multiplication - Build the method multiplication that multiplies num1 by num2 and returns the result of this calculation
• division - Build the method division that divides num2 into num1 and returns the result of this calculation
• modulo - Build the method modulo that divides num2 into num1 and gives us the remainder of this calculation
• square_root -- Build the method square_root that finds the square root of num and returns the result

Use Methods Provided by Ruby

If a few places we've asked specific instances of data to run methods (.class or .to_s) on themselves. Or you might have seen some code on the internet do this.

We call those methods instance methods. We're asking a given number, say 314 for its .class (314.class #=> Integer).

But sometimes Ruby provides standard helpful functions as class methods. A class method is like a utility method that's contained in a special namespace. Let's say you needed to do some trigonometry. Ruby has you covered! You can use Math.sin() to find the sine of an angle. Ruby also provides Math.sqrt() as a class method so that you can use Ruby's understanding of squares to help out.

So, Math.sin(81) returns 9. You can "wrap" Math.sin in the implementation of your square_root method. Wrapping clunkily-named "standard" capabilities of a programming language is a surprisingly large part of a programmer's career.

This is scratching the surface of "Object-Oriented Programming." Helpful functions are available to instances and classes to help do work. There's a lot to say about this, but for the time being, we can use some class methods to help do some advanced mathematics.

Once all tests are passing, submit the lesson.

Conclusion

Ruby gives us many operators that can be used to perform calculations. This is the tip of the iceberg—we can do so much more than simple arithmetic; however, these operations are the most common that a developer will encounter. Grasping the basics will get you very far!