Ruby: Range Class

Question 1

Which construction for a range means INCLUSIVE of the final character?

A) ..
B) …

Answer 1

..

The two dot construction means INCLUSIVE of the final character.

Example:
(1..10)
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Question 2

Which construction for a range means EXCLUSIVE of the final character?

A) ..
B) …

Answer 2

…

The three dot construction means EXCLUSIVE of the final character.

Example:
(1…10)
=> [1, 2, 3, 4, 5, 6, 7, 8, 9]

Question 3

What the .begin method for a range do?

Answer 3

Returns the object that defines the beginning of the range.

Question 4

How can you return the first element of a range?

example

Answer 4

Using the begin method.

(1..10).begin

=> 1

Question 5

.min

Answer 5

Finds the minimum of the range.

Question 6

.max

Answer 6

Find the maximum of the range.

Question 7

.include?( )

Answer 7

Ask the range if it includes the object passed to it.

Question 8

.inject

Answer 8

Performs one action on the first two items of the range, then performs the action on the result of those two. Until all parts of range are used.

Question 9

.reject

Answer 9

Takes a code block. Returns an ARRAY of the part of the range that hasn’t been reject.

digits.reject { |i| i < 5} # => [5, 6, 7, 8, 9]

Question 10

Using Range as conditions

Answer 10

Ranges can be used as conditional expressions.

while line = gets
puts line if line =~ /start/ .. line =~ /end/
end

Question 11

Interval Test

Answer 11

===

The case equality operator is used to see whether some value falls within the interval represented by the range.

(1..10) === 5 # => true
(1..10) === 15 # => false
(1..10) === 3.14159 # => true
(‘a’..’j’) === ‘c’ # => true
(‘a’..’j’) === ‘z’ # => false

Question 12

When is the === operator used most?

Answer 12

It’s called the case equality operator and is used most often with ….case statements.

car_age = gets.to_f # let's assume it's 5.2 case car_age
when 0...1
puts "Mmm.. new car smell" when 1...3
puts "Nice and new" when 3...6
puts "Reliable but slightly dinged" when 6...10
      puts "Can be a struggle"
    when 10...30
      puts "Clunker"
    else
puts "Vintage gem" end
produces:

Reliable but slightly dinged.

NOTE: Exclusive ranges (…) are normally used for case statements.