Ruby – the difference between Integer and Fixnum

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I know that the Fixnum class inherits from the Integer class. But what is the actual difference between them? Are there any use cases where we sometimes use Fixnum, and sometimes use Integer instead?

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UPDATE: As of Ruby 2.4, the Fixnum and Bignum classes are gone, there is only Integer. The exact same optimizations still exist, but they are treated as "proper" compiler optimizations, i.e. behind the scenes, invisible to the programmer.

This is somewhat confusing. Integer is the real class that you should think about. Fixnum is basically a performance optimization that should never have been made visible to the programmer in the first place. (Compare this with flonums in YARV, which are implemented entirely as an optimization inside the VM, and never exposed to the programmer.)

Basically, Fixnums are fast and Bignums are slow(er), and the implementation automatically switches back and forth between them. You never ask for one of those directly, you will just get one or the other, depending on whether your integer fits into the restricted size of a Fixnum or not.

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Ruby – the “right” way to iterate through an array in Ruby

This will iterate through all the elements:

array = [1, 2, 3, 4, 5, 6]
array.each { |x| puts x }

Prints:

This will iterate through all the elements giving you the value and the index:

array = ["A", "B", "C"]
array.each_with_index {|val, index| puts "#{val} => #{index}" }

Prints:

A => 0
B => 1
C => 2

I'm not quite sure from your question which one you are looking for.

Ruby – the difference between include and require in Ruby

What's the difference between "include" and "require" in Ruby?

Answer:

The include and require methods do very different things.

The require method does what include does in most other programming languages: run another file. It also tracks what you've required in the past and won't require the same file twice. To run another file without this added functionality, you can use the load method.

The include method takes all the methods from another module and includes them into the current module. This is a language-level thing as opposed to a file-level thing as with require. The include method is the primary way to "extend" classes with other modules (usually referred to as mix-ins). For example, if your class defines the method "each", you can include the mixin module Enumerable and it can act as a collection. This can be confusing as the include verb is used very differently in other languages.

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So if you just want to use a module, rather than extend it or do a mix-in, then you'll want to use require.

Oddly enough, Ruby's require is analogous to C's include, while Ruby's include is almost nothing like C's include.

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Ruby – the “right” way to iterate through an array in Ruby

Ruby – the difference between include and require in Ruby

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