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Learning Goals

  1. Become familiar with a REPL environment
  2. Learn about the fundamentals of programming
  • Numbers + Basic Mathematic Operations
  • Data Types
  • Variables
  • Methods
  • Logical Operations

Getting Started

  1. Open https://repl.it/
  2. Please search for and choose the language Ruby
  3. Type in puts "Hello, World!" + click run

Note:

Talk to them about what puts does Make sure to note that printing out words require quotation marks around the word Mention that words are known as strings and letters are known as chars

Congratulations, you just ran your first program

congratulations

R-E-P-L

  • Read - Evaluate - Print - Loop
  • Interactive computer programming environment that takes single user inputs (i.e. single expressions), evaluates them, and returns the result to the user

Note:

"Now that we have an environment we can all work in, let's get down to the basics"

Coding Basics

Numbers

  • Integers vs Floats
    • 1 vs 1.0
  • No commas in long integers!
  • +, -, *, /, %
    • /: rounds down
    • %: modulo operation => remainder
  • Order of Operations still applies!

Number Practice

puts 2 + 5
puts 2 - 5
puts 2 * 5
puts 2 / 5
puts 2.0 / 5.0
puts 2 % 5
puts (2+5) * 6 / 3

More Division + Modulo Practice

puts 25 / 4
puts 1 / 17
puts 0 / 17

puts 24 % 5
puts 1 % 4
puts 0 % 8

Data Types

  • Numbers
    • integers, floats
  • Strings
    • letters, words, characters
  • Boolean
    • true, false
  • Nil
    • a word to describe absence of data or emptiness

Data Conversion / Coercion

  • to_i => to integer
  • to_s=> to string
puts "5" + "5"
puts "5".to_i + "5".to_i
puts (5 + 5).to_s
puts 5.to_s + 5.to_s
puts "5" + 5
puts "5" * 5

Before Variables

Let's say we want to print out Hello, World! three times.

puts "Hello, World!"
puts "Hello, World!"
puts "Hello, World!"

After Variables

Let's shorten the amount of code, by storing the string in variable

phrase = "Hello, World!"
puts phrase
puts phrase
puts phrase

Variables

  • A variable name consists of letters and numbers
  • The first character needs to be a (lowercase) letter
  • Variables must not contain spaces.
  • When the name of a variable consists of multiple words, it is Ruby convention to separate the words with a _
  • The value assigned to the variable can change over time
  • = is the assignment operator => you can use it to assign or re-assign values to variables

Methods

  • Methods are the "verbs" of Ruby. Numbers and strings are the objects or "nouns"
  • When you call or invoke a method, it does something to one or more objects
  • When we call a method, we always use the format object.method
    • To the left of the dot is the noun, to the right of the dot is the verb
"7".to_i
42.to_s

Comparison Operations

  • <
  • >
  • !
  • ==
  • !=

Note:

Mention common mistake between = and ==

REPL IT

puts 2 < 5
puts 2 > 5
puts 2 == 5
puts 2 != 5
puts 5 == "5"
puts "a" < "b"
puts !true
puts !false

Note:

They will do that in their own REPL environments for slides with this title

Review

  • REPL
  • +, -, *, /, %
  • Data Types
  • Variables and Methods
  • <, >, !, ==, !=