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Ruby nested until loop with examples

Nested until loop in Ruby: In this tutorial, we are going to learn about the nested until loop in Ruby programming language with syntax and examples.
Submitted by Hrithik Chandra Prasad, on August 05, 2019

Nested until loop

Alike for, while, and do...while, until loop can also be nested for meeting the specific purpose. In this type of nesting, two until loops work in the combination such that at first, the outer loop is triggered which results in the execution of the inner loop. The outer Until loop is not invoked as long as the inner loop does not comes out to be true. It is a kind of Entry control loop which simply means that first the outer Boolean expression is processed; if it is false then the pointer will move to the inner loop to check inner condition. The whole execution will take place in the same manner.

Syntax:

    until conditional [do]
        until conditional [do]
            # code to be executed
        end       
        # code to be executed
    end

Example 1:

=begin 
Ruby program to find the sum of numbers lying 
between two limits using nested until loop
=end

puts "Enter the Upper limit"
ul=gets.chomp.to_i
puts "Enter the Lower limit"
ll=gets.chomp.to_i

until ul==ll
	num=ul
	temp=ul
	sum = 0

	until num==0
		#implementation of until loop
		rem=num%10
		num=num/10
		sum=sum+rem
	end

	puts "The sum of #{temp} is #{sum}"
	ul=ul-1
end

Output

Enter the Upper limit
1000
Enter the Lower limit
980
The sum of 1000 is 1
The sum of 999 is 27
The sum of 998 is 26
The sum of 997 is 25
The sum of 996 is 24
The sum of 995 is 23
The sum of 994 is 22
The sum of 993 is 21
The sum of 992 is 20
The sum of 991 is 19
The sum of 990 is 18
The sum of 989 is 26
The sum of 988 is 25
The sum of 987 is 24
The sum of 986 is 23
The sum of 985 is 22
The sum of 984 is 21
The sum of 983 is 20
The sum of 982 is 19
The sum of 981 is 18

Example 2:

Pattern printing: Print the following pattern

    0
    01
    012
    0123
    01234

Code:

=begin 
Ruby program to print the given pattern.
=end

num=0

until (num==6)
	j=0
	until(j==num)
		print j
		j+=1
	end
	puts ""
	num+=1
end