Ruby_Lesson_Looping with Ruby

1.The 'While' Loop
we use something called a while loop. It checks to see if a certain condition is true, and while it is, the loop keeps running. As soon as the condition stops being true, the loop stops!
2.Danger: Infinite Loops!
infinite loop and it will cause your programs to crash. Avoid them at all costs!
i = 0
while i < 5
  puts i
  i = i+1 
end
3.The 'Until' Loop

The complement to the while loop is the until loop. It's sort of like a backwards while:

i = 0
until i == 6
  i += 1
end
puts i

1. In the example above, we first create a variable i and set it to zero.
2. Then we execute a block of code until i is equal to 6. That block of code increments i.
3. When i is equal to 6, the block ends.
4. Finally, we print 6, the value of i, to the console.

4. More Assignment Operators
A shortcut is to use an assignment operator.  You can update a variable with additional assignment operators, however, which include +=, -=, *=, and /=.
counter = 1
while counter < 11
  puts counter
  counter += 1
end
'For' Loops
5.The 'For' Loop
for num in 1...10
  puts num
end
6. Inclusive and Exclusive Ranges
The reason Ruby counted to 9 and not 10 was because we used three dots in the range; this tells Ruby to exclude the final number in the count: for num in 1...10 means "go up to but don't include 10." If we use two dots, this tells Ruby to include the highest number in the range.
Iterators & Blocks
8.The Loop Method
It's also possible to repeat an action using an iterator.
The simplest iterator is the loop method. You can create a basic (but infinite!) loop by simply typing

loop { print "Hello, world!" }

In Ruby, curly braces ({}) are generally interchangeable with the keywords do (to open the block) and end (to close it). Knowing this, we can write a smarter loop than the one above:

i = 0
loop do
  i += 1
  print "#{i}"
  break if i > 5
end

The break keyword is our Get Out of Jail Free card: it breaks a loop as soon as its condition is met.
9.Next!
The next keyword can be used to skip over certain steps in the loop. For instance, if we don't want to print out the even numbers, we can write:

for i in 1..5
  next if i % 2 == 0
  print i
end

10.Saving Multiple Values
In Ruby, we can pack multiple values into a single variable using an array. An array is just a list of items between square brackets, like so: [1, 2, 3, 4]. The items don't have to be in order—you can just as easily have [10, 31, 19, 400].
my_array = [1,2,3,4,5]
11.The .each Iterator
A more useful iterator is the .each method, which can apply an expression to each element of an object, one at a time. The syntax looks like this:

object.each { |item| # Do something }

You can also use the do keyword instead of {}:

object.each do |item| # Do something end

The variable name between | | can be anything you like: it's just a placeholder for each element of the object you're using .each on.
array = [1,2,3,4,5]
array.each do |x|
  x += 10
  print "#{x}\n"
end
12.The .times Iterator
The .times method is like a super compact for loop: it can perform a task on each item in an object a specified number of times.
For example, if we wanted to print out "Chunky bacon!" ten times, we might type

10.times { print "Chunky bacon!" }

13.Project
13.1.Getting the User's Input
puts "text"
text = gets.chomp
puts "redact"
redact = gets.chomp

13.2.The .split Method
Ruby has a built-in method for this called .split; it takes in a string and returns an array. If we pass it a bit of text in parentheses, .split will divide the string wherever it sees that bit of text, called a delimiter. For example,

text.split(",")

tells Ruby to split up the string text whenever it sees a comma.

13.3.Redacted!
Let's start simple: write an .each loop that goes through words and just prints out each word it finds.
words.each do |word|
    print word
end
13.4.Control Flow Know-How

1. if the current word equals the word to be redacted, then print "REDACTED " with that extra space.
2. Otherwise (else), print word + " ".

 if word == redact
        print "REDACTED "
    else
        print word+" "
    end