Chapter 3

Question 1

Expression?

Answer 1

Combination of numbers, operators and variables that, when understood by the computer, result in an answer of some form.

Question 2

Number Comparison Operators in Ruby?

Answer 2

x > y Greater than
x < y Less than
x == y Equal to
x >= y Greater than or equal to
x <= y Less than or equal to
x <=> y Comparison; returns 0 if x and y are equal, 1 if x is higher, and −1 if y is higher
x != y Not equal to

Question 3

Basic loop

Answer 3

.times 5.times

Question 4

Iterator

Answer 4

Progresses through a list of items one by one. ..or different multiples:

.each

1. upto(5)
2. downto(5)
3. step(50, 5)
4. upto(5) { |number| puts number }

Question 5

String Literal

Answer 5

When a string is embedded directly into code, using quotation marks.

Question 6

Interpolation

Answer 6

Embedding expressions and even logic into strings

x = 10 y = 20

puts “#{x} + #{y} = #{x + y}”

Question 7

String Methods


Answer 7

Question 8

Regular Expression

Answer 8

is a string that describes a pattern for matching elements in other strings.

Question 9

Operator

Answer 9

Something that’s used in an expression to manipulate objects such as+(plus), - (minus), * (multiply), and / (divide). You can also use operators to do comparisons, such as with <, >, and &&.

Question 10

Arrays

Answer 10

A collection of objects or values with a defined, regular order.

x = [1, 2, 3, 4]

Question 11

Array Index

Answer 11

position within the array.

Question 12

Array Literal

Answer 12

Square brackets are used to denote an array literal.

Question 13

Array Element Reference

Answer 13

To access a particular element, an array (or a variable containing an array) is followed by the index contained within square brackets.

puts x[2]

Question 14

Array <<

Answer 14

is the operator for pushing an item onto the end of an array. It’s equivalent to the push method.

Question 15

Array Push

Answer 15

equivalent to <<
x.push(“word”)

Question 16

Array Pop

Answer 16

is the process of retrieving and removing items from the end of the array.

x = []
x << “Word”
x << “Play”
x << “Fun”
puts x.pop
puts x.pop
puts x.length

Fun
Play
1

Question 17

Hash

Answer 17

A collection of objects or values associated with keys. A key can be used to find its respective value inside a hash, but items inside a hash have no specific order. It’s a lookup table, much like the index of a book or a dictionary.

dictionary = { ‘cat’ => ‘feline animal’, ‘dog’ => ‘canine animal’ }

Question 18

Regular Expresion

Answer 18

A way to describe patterns in text that can be matched and compared against.

Question 19

Code block

Answer 19

A section of code, often used as an argument to an iterator method, that has no discrete name and that is not a method itself, but that can be called and handled by a method that receives it as an argument

Question 20

Range

Answer 20

The representation for an entire range of values between a start point and an endpoint.

(‘A’..’Z’).to_a.each { |letter| print letter }

Question 21

Symbol

Answer 21

A unique reference defined by a string prefixed with a colon (for example, :blue or :name). Symbols don’t contain values as variables do, but can be used to maintain a consistent reference within code.
person1 = { :name => “Fred”, :age => 20, :gender => :male }

You might want to consider symbols to be literal constants that have no value, but whose name is the most important factor.

Question 22

Substitutions

Answer 22

puts “foobar”.sub(‘bar’, ‘foo’)

gsub does multiple substitutions at once, as this example demonstrates: puts “this is a test”.gsub(‘i’, ‘’)

x = “This is a test” puts x.sub(/^../, ‘Hello’)

Question 23

.scan

Answer 23

example. What if you want to iterate through a string and have access to each section of it separately? scan is the iterator method you require:

“xyz”.scan(/./) { |letter| puts letter } x y z

Question 24

Basic Special Characters and Symbols Within Regular Expressions


Answer 24

Question 25

Regular Expression Character and Sub-Expression Modifiers

Answer 25

Question 26

.each

Answer 26

[1, “test”, 2, 3, 4].each { |element| puts element.to_s + “X” }

Question 27

.collect

Answer 27

Although each iterates through elements of an array, you can also convert an array on the fly using the collect method:

[1, 2, 3, 4].collect { |element| element * 2 } [2, 4, 6, 8]

Question 28

Flow Control

Answer 28

age = 10
if age < 18
puts “You’re too young to use this system”
else
puts “You can use this system”
end

age = 10
unless age >= 18
puts “You’re too young to use this system”
puts “So we’re going to exit your program now”
exit
end

Question 29

Ternary Operator

Answer 29

makes it possible for an expression to contain a mini if/else statement.

age = 10 type = age < 18 ? “child” : “adult”

Question 30

Elseif

Answer 30

fruit = “orange”
if fruit == “orange”
color = “orange”
elsif fruit == “apple”
color = “green”
elsif fruit == “banana”
color = “yellow”
else
color = “unknown”
end

Question 31

Case Block

Answer 31

fruit = “orange”
case fruit
when “orange”
color = “orange”
when “apple”
color = “green”
when “banana”
color = “yellow”
else
color = “unknown”
end

Question 32

While

Answer 32

x = 1
while x < 100
puts x
x = x * 2
end

Question 33

Until

Answer 33

x = 1
until x > 99
puts x
x = x * 2
end