TECH 601-00 - Examples and Solutions

colors.rb

colors = ["purple", "yellow", "blue", "white", "red", "green", "orange"]

puts colors[4]
puts colors[40]
puts colors.index("green")
puts colors.index("foo")

colors2 = [
  ["tuesday", "purple"],
  ["saturday", "yellow"],
  ["wednesday", "blue"],
  ["sunday", "white"],
  ["monday", "red"],
  ["thursday", "green"],
  ["friday", "orange"]
]

# puts colors2[0].inspect
# puts colors2[0][1].inspect

colors2.each_with_index do |pair, index|
  puts "#{pair} at index #{index}"
  pair.each_with_index do |day, color|
    puts "#{day} is #{color}"
  end
end

colors3 = {
  "tuesday" => "purple",
  "saturday" => "yellow",
  "wednesday" => "blue",
  "sunday" => "white",
  "monday" => "red",
  "thursday" => "green",
  "friday" => "orange"
}

puts colors3["thursday"]

data.rb

# original data
# https://www.cisweb1.unr.edu/cxs/CourseListing.asp?master_id=1955&course_area=BASE&course_number=105&course_subtitle=00

data = File.read("data.txt")
lines = data.split("\n")

# puts line.inspect

course = {}

lines.each do |line|
  heading, content = line.split(":")
  
  puts "heading: #{heading}"
  puts "content: #{content}"
  
  course[heading] = content.to_s.strip
end

puts course.inspect

data.txt

Course:	BASE 105-00
Term:	2145
Section Number:	2
Schedule Number:	2145BASE1052
Instructor(s):	Jay Johnson, Mark Kertenian
Location:	William Peccole Park - UNR
Dates:	July 7 - 11, 2014 (Schedule TBA)
Units:	Non-Credit
Notes:	Additional Information
Upon registration, you will receive a confirmation via email, so please provide your email address during registration.
NEW THIS YEAR: All camp health forms, behavior guidelines, maps and other paperwork will be posted online for download at www.unr.edu/sportscamps. Please complete the health form and behavior form and return them as soon as possible.
Full payment is due upon registration. A $50 cancellation fee will be charged for participant-initiated cancellations made prior to camp. No refunds will be given after the start of camp.
Fee includes instruction, and camp t-shirt and hat.
 

exercise1.rb

# 1. create a variable named 'a' with the value of 1 and display 'a'
a = 1
puts a

# 2. create a variable named 'b' with the value of 2 and display 'b'
b = 2 
puts b 

# 3. create a variable named 'c' with the value of 3 and display 'c'
# 4. create a variable named 'd' with the value of 10 and display 'd'
# 5. add 'a' and 'b' and display the result
# 6. add 'a' and 'd' and display the result
# 7. add 'a' and 'b' and 'c' and 'd' and display the result
# 8. multiply 'd' and 'b' and display the result
# 9. multiple 'd' by itself and display the result
# 10. divide 'd' by 'b' and display the result
# 11. divide 'd' by itself and display the result
# 12. create a list named 'lots_of_a' that contains 4 'a's
# 13. display contents of the list 'lots_of_a'
# 14. create a list named numbers that contains 'a', 'b', 'c', and 'd'  and display the list
# 15. create a variable named 'name' that contains your full name
# 16. create a variable named 'greeting' that contains the words "Hello, my name is: "
# 17. create a varialbe named 'full_greeting' that is made up of 'greeting' and 'name' and display the result
# 18. iterate through 'numbers' and display "The value is: " with each value
# 19. get the sum of 'numbers' and display the result
# 20. get the average of 'numbers' and display the result

# BONUS - What happens if you try to run the following (and why)?:
#               "1" + 1
#         What could we do to make that run?

exercise1_solutions.rb

# 1. create a variable named 'a' with the value of 1 and display 'a'
a = 1
puts a

# 2. create a variable named 'b' with the value of 2 and display 'b'
b = 2
puts b

# 3. create a variable named 'c' with the value of 3 and display 'c'
c = 3
puts c

# 4. create a variable named 'd' with the value of 10 and display 'd'
d = 10
puts d

# 5. add 'a' and 'b' and display the result
result = a + b
puts result

# 6. add 'a' and 'd' and display the result
puts a + d

# 7. add 'a' and 'b' and 'c' and 'd' and display the result
puts a + b + c + d

# 8. multiply 'd' and 'b' and display the result
puts d * b

# 9. multiple 'd' by itself and display the result
puts d * d

# 10. divide 'd' by 'b' and display the result
puts d / b

# 11. divide 'd' by itself and display the result
puts d / d

# 12. create a list named 'lots_of_a' that contains 4 'a's
lots_of_a = [a, a, a, a]

# 13. display contents of the list 'lots_of_a'
puts lots_of_a

# 14. create a list named numbers that contains 'a', 'b', 'c', and 'd'  and display the list
numbers = [a, b, c, d]
puts numbers

# 15. create a variable named 'name' that contains your full name
name = "Phil"

# 16. create a variable named 'greeting' that contains the words "Hello, my name is: "
greeting = "Hello, my name is: "

# 17. create a varialbe named 'full_greeting' that is made up of 'greeting' and 'name' and display the result
full_greeting = greeting + name
puts full_greeting

# 18. iterate through 'numbers' and display "The value is: " with each value
for number in numbers
  "The value is: #{number}"
end

numbers.each do |number|
  "The value is: #{number}"
end

numbers.each { |number| "The value is: #{number}" }

# 19. get the sum of 'numbers' and display the result
sum = 0
numbers.each do |number|
  sum = sum + number
end
puts "Sum: #{sum}"

sum = 0
numbers.each do |number|
  sum += number
end
puts "Sum: #{sum}"

sum = numbers.reduce(0) { |counter, number| counter += number }
puts "Sum: #{sum}"

# 20. get the average of 'numbers' and display the result
sum = numbers.reduce(0) { |sum, num| sum += num }
count = numbers.size
puts "Average: #{sum / count}"

# BONUS - What happens if you try to run the following (and why)?:
#               "1" + 1
#         What could we do to make that run?
s1 = "1"
n1 = 1
puts ".to_s - #{s1 + n1.to_s}"
puts ".to_i - #{s1.to_i + n1}"

exercise2.rb

# 1. assign the string "5" to a variable and display the value
 
# 2. assign the integer 5 to a variable and display the value
 
# 3. add the two variables by coercing the first value to an integer, assign 
#    that value to a variable, and display the value
 
# 4. add the two variables by coercing the second value to a string, assign 
#    that value to a variable, and display the value
 
# 5. create an array which holds the previous values
 
# 6. use a `for` loop to display each value in the array
 
# 7. add your name to the end of the array
 
# 8. use `each` to iterate through each value in the array, display the value
 
# 9. display the value with your name
 
# 10. add the string "example" to the beginning of the array
 
# 11. display the value with "example"
 
# 12. use `each` to iterate through each value in the array, display each value
#     along with the data type. Example: "Value: example - Type: String"
#     following: "Value: "
 
# 13. assign your name to a variable
 
# 14. assign your favorite color to a variable
 
# 15. create a hash with the keys "name" and "color" with the values from the 
#     variables above
 
# 16. using values from the hash above, display the following: 
#     "My name is Phil and my favorite color is Green."
 
# 17. create another hash with values for a friend of yours
 
# 18. create a new array using the people hashes above as values
 
# 19. iterate through the array of people, display the following for each:
#     "My name is X and my favorite color is Y."

exercise2_solutions.rb

# 1. assign the string "5" to a variable and display the value
a = "5"
puts a

# 2. assign the integer 5 to a variable and display the value
b = 5
puts b

# 3. add the two variables by coercing the first value to an integer, assign 
#    that value to a variable, and display the value
c = a.to_i + b
puts c

# 4. add the two variables by coercing the second value to a string, assign 
#    that value to a variable, and display the value
d = a + b.to_s
puts d

# 5. create an array which holds the previous values
array = [a, b, c, d]
puts array

# 6. use a `for` loop to display each value in the array
for item in array
  puts item
end

# 7. add your name to the end of the array
array[4] = "Phil"
# or
# array.push("Phil")
# or
# array << "Phil"

# 8. use `each` to iterate through each value in the array, display the value
array.each do |item|
  puts item
end

# 9. display the value with your name
puts array[4]

# 10. add the string "example" to the beginning of the array
array.unshift("example")

# 11. display the value with "example"
puts array[0]

# 12. use `each` to iterate through each value in the array, display each value
#     along with the data type. Example: "Value: example - Type: String"
#     following: "Value: "
array.each do |item|
  puts puts "Value: #{item} - Type: #{item.class}"
end

# 13. assign your name to a variable
name = "Phil"

# 14. assign your favorite color to a variable
color = "Green"

# 15. create a hash with the keys "name" and "color" with the values from the 
#     variables above
phil = {
  "name" => name,
  "color" => color
}

# 16. using values from the hash above, display the following: 
#     "My name is Phil and my favorite color is Green."
phrase = "My name is #{phil["name"]} and my favorite color is #{phil["color"]}."
puts phrase

# 17. create another hash with values for a friend of yours
don = {
  "name" => "Don",
  "color" => "Pink"
}

# 18. create a new array using the people hashes above as values
people = [phil, don]

# 19. iterate through the array of people, display the following for each:
#     "My name is X and my favorite color is Y."
people.each do |person|
  puts "My name is #{person["name"]} and my favorite color is #{person["color"]}."
end

exercise3.rb

# Remember: use `ruby exercise3.rb` to run this file

# 1. display the contents of the `my_variable` variable
my_variable = "100"

# 2. assign the integer 5 to a variable named 'number'

# 3. display the contents of the 'number' variable

# 4. change (coerce) the string in 'my_variable' into an integer

# 5. put the coerced string, now an integer, into a variable named 'new_number'

# 6. display the contents of the 'new_number' variable

# 7. add 'number' to 'new_number' and assign it to a variable named 'sum'

# 8. create an array with the values 1, 2, 4, and 5, assign it to a variable named `numbers`

# 9. display the contents of the array at index 1

# 10. display array element (contents) at index 10

# 11. use `each_with_index` to display the number and index for the `numbers` array

# 12. put a comment here that says what kind of operation `each_with_index` is
#   Hint: comments start with a `#`

# 13. create a hash with the keys of one, two, three, four, five and the values of 1, 2, 3, 4, 5
#   Hint: "one" => 1

# 14. use `each` to display the key and value for each member of the hash
#  Question: did you remember to put the hash in a variable?

# 15. change the display of the hash to say:
# "The value of 'one' is 1" for each member of the hash, so 'two' is 2, and 'three' is 3, etc.

exercise3_solutions.rb

# Remember: use `ruby exercise3.rb` to run this file

# 1. display the contents of the `my_variable` variable
puts "# 1. display the contents of the `my_variable` variable"

my_variable = "100"
puts my_variable

# 2. assign the integer 5 to a variable named 'number'
puts "# 2. assign the integer 5 to a variable named 'number'"

number = 5

# 3. display the contents of the 'number' variable
puts "# 3. display the contents of the 'number' variable"

puts number
# or
print number
# or
puts number.inspect

# 4. change (coerce) the string in 'my_variable' into an integer
puts "# 4. change (coerce) the string in 'my_variable' into an integer"

puts my_variable.to_i

# 5. put the coerced string, now an integer, into a variable named 'new_number'
puts "# 5. put the coerced string, now an integer, into a variable named 'new_number'"

new_number = my_variable.to_i

# 6. display the contents of the 'new_number' variable
puts "# 6. display the contents of the 'new_number' variable"

puts new_number

# 7. add 'number' to 'new_number' and assign it to a variable named 'sum'
puts "# 7. add 'number' to 'new_number' and assign it to a variable named 'sum'"

result = number + new_number + (5 - 7) * 9
puts result

# 8. create an array with the values 1, 2, 4, and 5, assign it to a variable named `numbers`
puts "# 8. create an array with the values 1, 2, 4, and 5, assign it to a variable named `numbers`"

numbers = [1,2,3,4,5]

# 9. display the contents of the array at index 1
puts "# 9. display the contents of the array at index 1"

puts numbers[1]

# 10. display array element (contents) at index 10
puts "# 10. display array element (contents) at index 10"

puts numbers[10].inspect

# 11. use `each_with_index` to display the number and index for the `numbers` array
puts "# 11. use `each_with_index` to display the number and index for the `numbers` array"

numbers.each_with_index do |number, index|
  puts number, index # Remember you can give `puts` more than one thing
end

# 12. put a comment here that says what kind of operation `each_with_index` is
#   Hint: comments start with a `#`
# iteration or looping
puts "# 12. put a comment here that says what kind of operation `each_with_index` is"

puts "# interation or looping"

# 13. create a hash with the keys of one, two, three, four, five and the values of 1, 2, 3, 4, 5
#   Hint: "one" => 1
puts "# 13. create a hash with the keys of one, two, three, four, five and the values of 1, 2, 3, 4, 5"

number_hash = {
  "one" => 1,
  "two" => 2,
  "three" => 3,
  "four" => 4,
  "five" => 5
}

# 14. use `each` to display the key and value for each member of the hash
#  Question: did you remember to put the hash in a variable?
puts "# 14. use `each` to display the key and value for each member of the hash"

number_hash.each do |key, value|
  puts key, value
end  

# 15. change the display of the hash to say:
# "The value of 'one' is 1" for each member of the hash, so 'two' is 2, and 'three' is 3, etc.
puts "# 15. change the display of the hash to say:"

number_hash.each do |key, value|
  puts "The value of '#{key}' is #{value + 10}"
end  

###############################################################################
# After working through the exercises we discussed other topics like:

## Variable Scope
puts "## Variable Scope"

# A variable created outside of the iteration block is available inside the
# block and after the block.
puts save_me = nil

numbers.each_with_index do |number, i|  
  save_me = number # assign the var here    
  puts "save_me is #{save_me}"
end

# save_me is availble here ... what is the value?
puts save_me


## Names of variables inside the pipes are arbitrary ...
puts "## Names of variables inside the pipes are arbitrary ..."

numbers.each_with_index do |a, n| # a & n instead of number & i
  puts a, n
end

# But it's a good idea to use names that are meaningful for the context ...
# Like name and index if the array is an array of names
names = ["Phil", "Don"]
names.each_with_index do |name, index|
  puts name, index
end

## Using different values for the key for a hash and the alignment of code.

# We could have made the keys for our hash the numbers instead of the text.
number_hash = {
  1 => "one",
  2 => "two",
  3 => "three",
  4 => "four",
  5 => "five",
  6 => "six",
  7 => "seven",
  11 => "eleven",
  400 => "fourhundred"
}

## Single quoted vs. Double quoted strings
puts "## Single quoted vs. Double quoted strings"

foo = "FOO"

# Single quotes don't allow interpolation.
name = '"Don #{foo}"'
puts name

# Double quotes allow interpolation.
name = "Don #{foo}"
puts name
puts name.inspect

# If we need to have interpolation and double quotes *in* the string we can use
# an arbitrary string delimeter like %()
last_name = "Cohen"
other_name = %("Phil \#{last_name}")
puts other_name
puts other_name.inspect

save_me.rb

numbers = [1,2,3,4,5]

save_me = nil

puts "save_me is #{save_me.inspect}"

numbers.each_with_index do |number, i|
  save_me = number
  puts "number is #{number}, index is #{i}"
  puts "save_me is #{save_me}"
end

puts "save_me is #{save_me}"