Strings

Question 1

How can you substitute double quotation marks?

Answer 1

With %Q
e.g.
%Q(It’s Tuesday now.)
=> “It’s Tuesday now.”

%q substitutes single quotes

Question 2

What do you use “casecmp” method for?

Answer 2

To compare the value of two strings while ignoring the case of both strings.
e.g.
name = ‘Roger’

puts name.casecmp(‘RoGeR’) == 0
puts name.casecmp(‘DAVE’) == 0

true
false

Question 3

What is string interpolation?

Answer 3

Invoking a variable (or a method) withing a string and Ruby automatically calls #to_s on the value.
e.g.
name = ‘Tom’
puts “Hello #{name}!”

=> Hello Tom!

Question 4

What does the following code return?

a=”Xyzzy”

def my_value(b)
b[2] = '-'
end
my_value(a)
pus a

Answer 4

Xy-zy, because it is assigned to b[2] rather than b.

Numbers are immutable, strings are mutable

Question 5

What does String#chars method do?

Answer 5

It returns an array of characters.
e.g.
def sum(num)
num.to_s.chars
end

puts sum(496)
=> ["4", "9", "6"]

Firstly convert a number to a string and then we created an array of characters.
Obviously it works directly on strings.

Question 6

What does the following method definition validate?

def integer?(input)
/^\d+$/(input)
end

Answer 6

It validates if the input is an integer or not.

^ means start of string
\d means regex to test against digits
+ means one or more (of the preceding matcher)
$ means end of string

Question 7

How do you access the following string’s last character?

pet = “dog”

Answer 7

pet[-1]

Question 8

What is String#chop used for?

Answer 8

It removes the string’s last character unconditionally.

e.g.
name = “Craig”
name = name.chop

name
=> Crai

Question 9

What does String#chomp do?

Answer 9

It conditionally removes the tail end of a string (defaulting in a new line).

Question 10

How does String#count work?

Answer 10

It gives as the number of characters we asked it to count.

e.g.
a = “danish banana”
a.count (“n”) => 3

a.count (“an”, “n”) =>3
(It only counts the intersection of the two strings)

a.count (“a-d”) => 6

Question 11

How does String#delete work (with examples)?

Answer 11

It deletes whichever characters we assign to it.

e.g.
a = “danish banana”
a.delete (“a-d”) => “nish nn”

a. delete (“an”) => “dish b”
a. delete (“an”, “n”) => “daish baaa”