Ruby Quiz 25.2.2021

Question 1

class ABC
  def xyz
   puts "xyz in ABC"
  end
end.     #for this code, which one is true?
1.ABC::new::xyz
2.ABC::new.xyz
3.ABC.new::xyz
4.ABC.new.xyz

Answer 1

1. ABC::new::xyz
2. ABC::new.xyz
3. ABC.new::xyz
4. ABC.new.xyz

all are true

output “xyz in ABC”

Question 2

Is the below Ruby code valid?

-> (a) {p a}[“Hello world”]

If so, what does it do? Explain your answer.

Answer 2

The -> operator creates a new Proc, which is one of Ruby’s function types. (The -> is often called the “stabby proc”.)

This particular Proc takes one parameter (namely, a). When the Proc is called, Ruby executes the block

puts a

Question 3

Which one is true?

my_lambda = -> { puts “Lambda called” }

a) my_lambda.call
b) my_lambda.()
c) my_lambda[]
d) my_lambda.===

Answer 3

All are true.

a) my_lambda.call
b) my_lambda.()
c) my_lambda[]
d) my_lambda.===

These methods are used to call the lambda

Question 4

Which of the following is true?
defining a regular expression:

a) Regexp.new( ‘string pattern’ [, options ] )
b) /string pattern/
c) %r{string pattern}
d) ->(x){string pattern}

Answer 4

First three syntax are true.

a) Regexp.new( ‘string pattern’ [, options ] )
b) /string pattern/
c) %r{string pattern}
d) ->(x){string pattern}

fourth one is lambda syntax

Question 5

What are the meaning of the following character ranges in Regular Expression?
\w
\d
\s

Answer 5

\w is equivalent to [0-9a-zA-Z_]

\d is the same as [0-9]

\s matches white space (tabs, regular space, newline)

Question 6

What are the meaning of the following character ranges in Regular Expression?
\W
\D
\S

Answer 6

\W anything that’s not in [0-9a-zA-Z_]

\D anything that’s not a number

\S anything that’s not a space

Question 7

What is the use of the method “named_capture” in Regexp?

Answer 7

It will return a hash representing information about named captures of rxp.

A key of the hash is a name of the named captures. A value of the hash is an array which is list of indexes of corresponding named captures.

/(?< foo >.)(?< bar >.)/.named_captures
#=> {"foo"=>[1], "bar"=>[2]}

Question 8

What is the use of “to_c” method in String?

Answer 8

It will return the complex form of the input sting.

‘9’.to_c #=> (9+0i)
‘2.5’.to_c #=> (2.5+0i)

Question 9

a = “ 3”

How you will get this string?(without concatenation)

“Ruby 3”

Answer 9

a = “3”
a.prepend(“Ruby “)
puts a

Question 10

What is the use of abs2 method in Complex class?

Answer 10

gives square of the result

Complex(5).abs2 =>25

Question 11

What is the alternative way of expressing ‘if not’.?

Answer 11

unless
# if !(aDay == 'Saturday' or aDay == 'Sunday')

	unless aDay == 'Saturday' or aDay == 'Sunday'
		daytype = 'weekday'
	else
		daytype = 'weekend'
	end
	return daytype

Question 12

How “loop” keywords can be used in Ruby?

Answer 12

loop do

end
=============================
i=0
loop {
	puts(arr[i])
	i+=1
	if (i == arr.length) then 
		break 
	end
}

Question 13

What is the difference between #remove_method and #undef_method?

Answer 13

#undef_method( )
removes all methods, including the inherited ones.

#remove_method( )
removesall  the methods, incase of inheritance, it leaves inherited methods.

Question 14

Is there an equivalent of “continue” in Ruby?

Answer 14

The Ruby next statement is used to skip loop’s next iteration. Once the next statement is executed, no further iteration will be performed.

The next statement in Ruby is equivalent to continue statement in other languages.

Question 15

How to display the inbetween values in a range?

print (1..7) #=> [1, 2, 3, 4, 5, 6, 7]

Answer 15

entries, to_a

Question 16

What is the difference between last and max methods in Range?

Answer 16

1. .10.last=> “10”

1. ..10.max => “9”

Question 17

How can you resolve name conflict(same name in mixin modules) in modules?

Answer 17

alias_method.

module Happy

	def expression
		return "smiling"
	end
	alias happyexpression expression
end

Question 18

What each_pair method will do? Which class it belongs to?

Answer 18

take pair from a Hash, Hash class

h = { “a” => 100, “b” => 200 }
h.each_pair {|value| puts value }

Question 19

def sum(array)
  sum = 0
  array.each do |number|
    sum += number
  end
  return sum 
end 
p sum([5, 10, 20])
# => 35

Refactor this code using reduce method

Answer 19

def sum(array)
array.reduce(:+)
end
p sum([5, 10, 20])

The ‘reduce’ method can be used to take an array and reduce it to a single value.

Question 20

How can we print the minimum and maximum value from an array using a single method?

Answer 20

minmax

Return both minimum and maximum values from an array

puts [2,4,55,0,45].minmax