Ruby syntax lesson notes

# Strings
"hello 1 world"
p "hello 2 world"
p 'hello 3 world' 
p 4

# Booleans, variables and symbols
p true
p false
my_string_variable = "hello world"
p my_string_variable
my_boolean = true
p my_boolean
a, b = 1, 2
p :hello
p :hi123
p :HELLO

# Math Operations
p 1 + 2
p 5 - 1
p 6/2
p 4*3
p 2 ** 3
p "using variables for math"
x = 10
p x
x = x + 5
p x
x += 5
p x
p "less than and greater than"
p 4 > 5
p 3 < 6
p 5> 5
p 4 == 5
p 3 == 3
p "greater than or equal"
p 4 >= 4
p 5 >= 999
p "order of operations"
p ( 3+4) *7
p 3 + 4 * 7
sum = 3 + 4
p sum * 7
p "variables and comparisons"
wins = 11
losses = 5
p wins > losses
p wins == losses
p "strings and operations"
hello ="hello"
p hello * 3
p hello + " world"
p "string interpolation"
p "hello #{3}"
num = 5
p "hello #{num}"
p "3 + 4 = #{3+4}"
num1 = 3
num2 = 4
p "3 + 4 = #{num1 + num2}"
p "Here is a symbol: #{:easy}"
p "#{num1} + #{num2} = #{num1 + num2}"
# Compound Interest calculation
principal = 10_000
rate = 0.05
time = 5
num = 12
amount = principal * (1+ rate/num) ** (num*time)
p "After #{time} years I'll have #{amount} dollars"

# Nil
p "Bloc"[7]
p "Bloc"[2]
nilly = nil
p nilly

# Methods
def hello
  "Hello world"
end
p hello
def return_three
  a = 1
  b = 2
  a + b
end
p return_three
# num = number of times compounded
def compound_interest(name, principal, rate, years, num)
  amount = principal * (1 + rate/num) ** (num * years)
  "After #{years} years, #{name} will have #{amount} dollars!"
end
p compound_interest("Bob", 100, 0.05, 40, 12)
p compound_interest("Joelle", 250, 0.06, 50, 12)
# my link method
def link(site_address, site_name)
  "<a href='#{site_address}'>#{site_name}</a>"
end
p link("www.mysite.com", "My Site!")
# implicit and explicit parens
p "Hey there"
p("Hey there")