Float index on arrays

Explanation

This Ruby code creates an array a containing three elements: 21, 42, and 84.

Then, it accesses the element at index 1.2 of the array a.

Normally, in most programming languages, array indices are integers, so accessing an array element with a floating-point number might seem unusual.

However, in Ruby, this is allowed...

When using a floating-point number as an index to access an array, Ruby will truncate the decimal part of the number and treat it as an integer index.

In this case, a[1.2] evaluates to a[1], because 1.2 truncated to an integer becomes 1.

Therefore, the code a[1.2] returns the element at index 1 of the array a, which is 42.

Voilà!