Upto and downto methods in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the upto method do in Ruby?

The upto method counts from a starting number up to an ending number, running a block of code for each number in that range.

beginner

How does the downto method work in Ruby?

The downto method counts down from a starting number to an ending number, running a block of code for each number in that range.

beginner

Example: What will this code print?<br>

5.upto(7) { |n| puts n }

It will print:<br>5<br>6<br>7<br>Because upto counts from 5 up to 7, printing each number.

beginner

Example: What will this code print?<br>

3.downto(1) { |n| puts n }

It will print:<br>3<br>2<br>1<br>Because downto counts down from 3 to 1, printing each number.

beginner

Can upto and downto be used without a block?

No, both methods require a block to tell Ruby what to do with each number in the count. Without a block, they do nothing.

What does 2.upto(4) { |n| puts n } print?

A 2 3 4

B 4 3 2

C 2 4

D Nothing

The upto method counts up from 2 to 4, printing each number.

Which method counts down from a number to a smaller number?

A upto

B times

C downto

D each

downto counts down from a starting number to an ending number.

What happens if you call 5.upto(3) { |n| puts n }?

A Prints 5, 4, 3

B Prints nothing

C Prints 3, 4, 5

D Raises an error

Since 5 is greater than 3, upto does not run the block and prints nothing.

Which of these is true about downto?

A It counts up

B It can be used without a block

C It only works with strings

D It requires a block

downto requires a block to specify what to do for each number.

What will 1.upto(1) { |n| puts n } print?

A 1

B Nothing

C 1 2

D Error

It prints 1 because upto includes the end number.

Explain how the upto method works and give a simple example.

Think about counting forward like climbing stairs.

Describe the difference between upto and downto methods.

One goes up, the other goes down.