Learn Ruby - Arrays, Conditionals, Loops

[1, 2]

Each value in the Array must be separated with a comma.

[]
# OR
Array.new()

[] is called the empty array.

["mike tyson", 89, 9.7]

This array contains a String, Integer and Floating point number.

students is a variable that is assigned the array value ["mary", "kathy", "frank"]. The students array is composed of three different Strings.

3

length() is a method that is available to all arrays and returns the number of elements in the array.

Yes, variables can be used inside of Arrays.

lyric[0]

Arrays are zero-indexed so 0 gets the first element, 1 gets the second element, 2 gets the third element, etc.

lyric[-1]
# OR
lyric[2]

The last element of the lyric array is the String "free". Negative numbers can be used to index starting from the end of the array or we can simply use 2 to get the third element of the array.

ruff << "open up shop"
# OR
ruff.<<("open up shop")
# OR
ruff.push("open up shop")

<<() and push() are build in methods to arrays and they follow the standard syntax: array, followed by dot, followed by whatever is being added to the array.

true

== is a boolean operator to compare if two values are the same. If two values are the same, == returns true, and if the two values are not the same, == returns false.

This raises an error because true is a special reserved keyword in Ruby and cannot be used as a variable. false is also a special reserved keyword.

"matt" == "matt"

This expression returns true because "matt" and "matt" are the same String.

false

!= is a boolean operator that stands for "does not equal". The statement "4 does not equal 4" is not true, so the expression returns false.

true

> is the "greater than" operator. 5 is greater than 4, so the expression evaluates to true.

Since 5 > 4 evaluates to true, the code inside the if block will be executed and "5 is greater than 4" will be printed. If 5 > 4 did not evaluate to true, then the code in the if block would not be executed.

"5 is not less than 4"

Since 5 < 4 is not true, the code inside the if block is not executed. The code inside the else clause is executed when the boolean condition (5 < 4) does not evaluate to true (aka when the boolean condition evaluates to false).

"matt equals matt"

The elsif keyword is used to add additional logical criteria to an if statement and this expression prints "matt equals matt". In this case, the boolean condition following the if statement ("sam" == "cat") evaluates to false, so the code inside the if block is not executed. However, the boolean condition following the elsif statement evaluates to true ("matt" == "matt"), so the code inside the elsif block is executed.

This expression prints "Hello there". This example is confusing because the value after if is the number 5, not a boolean condition. In Ruby, "truthy" and "falsey" values can be used in place of boolean conditions. Every value in Ruby is truthy, except nil and false, which are falsey.

This expression prints "bob is truthy". Any value that is not nil or false is considered true in a boolean context, so "bob" is considered true. Therefore, the code in the if block is executed.

This expression prints "nil is falsey". nil is considered false in a boolean context, so the code in the else block is executed.

This expression prints "This syntax is cool" because true is considered true in a boolean context. This example has the same meaning, but is more concise than the typical syntax:

if true
  puts "This syntax is cool"
end

This expression prints nothing. The boolean condition is false, so the puts statement is never executed.

x equals 6. x was originally 5, but x was reassigned to be 5 + 1 or 6.

mode equals "chillhippie". The += notation is shorthand for the variable reassignment syntax we saw in the prior question. The following lines are equivalent:

mode += "hippie"
mode = mode + "hippie"

"Went through the loop"
"Went through the loop"
"Went through the loop"

This is an example of a while loop. The variable counter is initially set to zero and the code inside the while loop is executed whenever the boolean condition (counter < 3) is true. For the first loop, the boolean condition is true (0 < 3), so the string "Went through the loop" is printed and the counter variable is incremented (counter variable points to value of 1 after first iteration). The boolean condition also evaluates to true for the second loop (1 < 3) and the third loop (2 < 3), but it evaluates to false for the fourth loop (3 < 3). When the boolean condition for a while loop evaluates to false, the loop is exited.

This loop does not print anything because the boolean condition (3 > 15) never evaluates to true. Since the boolean condition never evaluates to true, the code inside the loop is never executed.

This will print "This is the song that never ends" infinitely and will never stop until the program is forced to quit. The boolean condition is always true, so the loop is never exited.

To exit the loop, press control + C