Programming as Conversation Part 3: Introduction

Learning Goals

• Define abstraction

Introduction

Before we jump into more code, let's think for a moment about something you encounter pretty much every day when you read a news article or email: the way we organize words to express and clarify meaning. For example, a paragraph is a collection of sentences, aligned by a topic sentence and bundled up or closed by a closing sentence. A paragraph can persuade or offend, direct, or explain. A paragraph has a function.

"Code paragraphs" are called, depending on language, "functions," "procedures," "methods," or "subroutines." They bundle up expressions and statements to accomplish a task. Just as "Make a Sandwich" encompasses specific, "atomic" actions like like "get slice of bread," "get jelly," etc., retrieve_avatar_image_for_user encompasses logic like if user_name == nil or if image_url == nil.

To have code that is easy to read, debug, and maintain, we need to bundle collections of atomic activities into "code paragraphs" that do work. Ruby calls these "methods."

Abstraction

This process of bundling up small atoms into a method is called "abstraction." "Abstraction" comes from the Latin word for "to pull away." When we're further away, many details are hard to see so only the most relevant shape of the general thing. For example, when you're on an airplane and are over a city the details of the mileage, what's in the cup holder, the make, or the model of the cars below are invisible, they're not essential. What is is the color of the little dots moving up and down the freeway. By abstracting we see what's more true generally.

Here's a few more "abstractions:"

• "Matt," "Lore," and "Mohawk" are atomic individuals, but we can refer to them all collectively by the abstraction, or they can be abstracted into "New Yorkers"
• Books about a killer dog, a scary alter ego, and a scary clown can be abstracted into the name "horror novels (by Stephen King)"
• Individuals with strange powers and (usually) strange clothing can be abstracted into "superheroes"

Abstraction is a natural part of learning to converse. When you're first learning to communicate, you don't know enough to start talking about abstractions. You prefer to think about real, visible, tangible things. But as you learn about opposites, how things are similar (and how perhaps one thing is dissimilar) you grow in your ability to abstract.

In fact, the thing that makes most higher learning "higher" is that the discussion, work, and discovery is focused on uncovering general principles that allow us to predict how things will work more-or-less most of the time. Amazingly, this was considered a pretty revolutionary idea at the time when Galileo and Newton started doing it. The moment that natural philosophers started looking for these "general rules of how things work," science as we know it was born.

Next Steps

Ruby calls bundles of statements that, together, accomplish a unit of work or process, methods. In Programming as Conversation 3 we'll learn to take our expressions and statements and bundle them up into abstractions called methods.

A New Way of Running Code: Tests and Labs

In Programming as Conversation 1, we learned to run code in IRB. In Programming as Conversation 2, we learned to run code by using ruby filename. When programmers need to run (and rerun, and rerun) code over and over, they like to use tests to run their code.

That's right, a test is Ruby code that runs Ruby code to verify the output. In this module, we're going to start giving you "Labs" to complete. We'll write the tests but you must write the code to satisfy the tests. When your tests pass you'll be able to move on through the module.

We believe that labs give you a chance to practice your skills. In Programming as Conversation Parts 1 and 2, we just wanted you to feel the magic and awesomeness of programming. We didn't want to crimp that joy with labs. But now you know enough to do some pretty powerful stuff. Tests will confirm for both you and us that you're really getting the hang of this stuff. That's such an awesome feeling, we can't wait to share it with you!

We have a specific lab that teaches how to solve a lab just a few lessons from now, so don't stress about it! We'll walk you through the first few and you're going to love getting the "green lights" just like the thousands of students who have come before you!