1_mary.rb

# From Spotlight, search for terminal
# From the terminal, type irb to start the Interactive Ruby shell
# To leave irb, type exit
# If shit gets weird, control-c

############################################
# Words for Mary
# Special words
# while, if, puts, do, end
# most others are variables or numbers
############################################


# Variables
a_number = 4
look_a_string = "string"
i = 0

# Puts
name = "Mary"
puts name

# Numbers and Math:
5 + 3
3 * 2
dexter_weight = 15.5
dresden_weight = 14
annie_weight = 12
total_cat_weight = dexter_weight + dresden_weight + annie_weight
number_of_cats = 3
average_cat_weight = total_cat_weight / number_of_cats
puts average_cat_weight

# Array and array.size
cat_weights = []
cat_weights << 15.5 << 14 << 12
#=> [15.5, 14, 12]
cat_weights[0]
#=> 15.5
cat_weights[1]
#=> 14
cat_weights.size
#=> 3

# Loop
i = 0
n = 10
while i < n
  i = i + 1
end
puts i
#=> 10

# Conditional
number_of_cats = 3
if number_of_cats > 4
  puts "holy shit you're nuts"
elsif number_of_cats == 3
  puts "you're pretty cool"
else
  puts "lame!"
end

2_mod.rb

# % is mod or remainder
12 % 5
#=> 2
15 % 5
#=> 0
15 % 10
#=> 5
5 % 10
#=> 5
100 % 10
#=> 0
100 % 5
#=> 0

4_loop_with_conditional.rb

# Loop with a conditional
i = 0
n = 10
sum_of_even_i = 0
while i < n
  if i % 2 == 0
    sum_of_even_i = i + sum_of_even_i
  end
  i = i + 1
end
puts sum_of_even_i

5_advanced_loop_with_array.rb

# Conditionals with a loop
cat_weights = []
cat_weights << 15.5 << 14 << 12
lightest_cat_weight = 0
i = 0
n = 3
while i < n
 if lightest_cat_weight == 0 || lightest_cat_weight < cat_weights[i]
    lightest_cat_weight = cat_weights[i]
  end
  i = i + 1
end
puts lightest_cat_weight

The cartoon/ visual way to learn ruby:

http://mislav.uniqpath.com/poignant-guide/