Ruby Infinity: How It Works & Why It Matters

What is infinity in Ruby?

It’s something that has a starting point but no ending.

In Ruby, we can express this concept of infinity with the Float::INFINITY constant.

You may be wondering how this is useful.

Let me explain with examples!

Infinity As A Result Of Arithmetic Operations

Ruby returns an Infinity object, as the result of certain math operations.

For example:

You may be familiar with the “division by zero” error.

Here it is:

# ZeroDivisionError: divided by 0


If you use a float, you get something else:

# Infinity


But that’s not all.

If you try a division of 0 by 0.0, then you get another special value.

Take a look:

# NaN

What is this NaN?

It means “Not a Number”, and as far as I know, this is the only place in Ruby where you’ll find this value.

Why is this a thing?

It’s part of the IEEE 754 Specification, which explains how floating-point operations should behave.

Btw, there are some related methods:

  • nan?
  • finite?
  • infinite?

You can use these methods to check for special values.

These methods are available on Floats.

Since Ruby 2.4 you can also use finite? & infinite? with Integers.

How to Create Infinite Ranges


That was interesting… let’s see more examples.

Now with Ranges!

Here’s an infinite range:

# [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

This can be helpful when you don’t know the end of the range in advance.

One problem…

It only works with numbers as the starting value.


# ArgumentError: bad value for range

What’s the solution?

With Ruby 2.6, you can do this:

# ["a", "b", "c", "d", "e"]

Yes, that’s not a mistake! This range has no ending value, only a starting value of "a", then two dots .. to make it a never-ending range.

This is new syntax.

Use Ruby 2.6+ if you want this to work.

Infinity As Maximum & Minimum Value

Another practical use for Infinity?


It’s the biggest (Infinity) & smallest (-Infinity) number in Ruby.

You can use this as a starting value.

Here’s an example:

def smallest_percent_size(style, ary_size)
  @smallest_percent ||= Float::INFINITY

  if style == :percent && ary_size < @smallest_percent
    @smallest_percent = ary_size


This code is from Rubocop, an open-source project.

Here's how it works:

We are trying to find the smallest array size, but we need a starting value for that because using nil would give you an error.

You could type a big number & hope that's enough.

Or you can use Float::INFINITY, knowing that's that biggest number possible.


You have learned about infinity in Ruby, what it is, where it may show up & how to use it.

Please share this article so more people can benefit from it.

Thanks for reading!