The latest features of Ruby backported to older versions.


Backports Library Gem Version

Yearning to use some of the new cool features in Ruby 2.5 while using 2.3.x? Have some legacy code in Ruby 1.8 but can't live without `flat_map`?

This gem is for you!

The goal of 'backports' is to make it easier to write ruby code that runs across different versions of Ruby.

Loading backports

Explicitly (recommended)

For example, if you want to use transform_values and transform_keys, even in Ruby implementations that don't include it:

require 'backports/2.4.0/hash/transform_values'
require 'backports/2.5.0/hash/transform_keys'

This will enable Hash#transform_values and Hash#transform_keys, using the native versions if available or otherwise provide a pure Ruby version.

By Module

To bring all the backports for a given Class/Module, you can specify only that Class:

require 'backports/2.3.0/hash'

This will make sure that Hash responds to dig, fetch_values, <, <=, >, >= and to_proc

Up to a specific Ruby version

You can load all backports up to a specific version. For example, to bring any version of Ruby mostly up to Ruby 2.4.0's standards:

require 'backports/2.4.0'

This will bring in all the features of 1.8.7 and many features of Ruby 1.9.x all the way up to Ruby 2.4.0 (for all versions of Ruby)!

While it is not recommended, you may `require 'backports/latest'` as a shortcut to the latest Ruby version supported. This is equivalent to the deprecated `require 'backports'`.

Note: Although I am a Ruby committer, this gem is a personal project and is not endorsed by ruby-core.

What's inside

Goals for backported features:

  1. Won't break older code

  2. Pure Ruby (no C extensions)

  3. Pass ruby/spec

Let's be a bit more precise about the “breaking code” business. It is of course entirely possible that code will break. In particular, you may be distinguishing parameters with duck typing, but a builtin class may, in the future, be responding to a particular call. Here's [an exemple from Rails]( that is relying on the fact that Proc and Method respond to :to_proc and Hash isn't. That is, until Ruby 2.3… This old version of Rails therefore won't work on Ruby 2.3, or on older Rubies with that the `2.3.0/hash/to_proc` loaded…

For Ruby < 2.0, there are some real incompatibilities. For example, Module::instance_methods which returns strings in 1.8 and symbols in 1.9. No change can be made without the risk of breaking existing code. Such incompatibilities are left unchanged, although you can require some of these changes in addition (see below).

Installation & compatibility

backports can be installed with:

gem install backports

To use:

require 'rubygems'
# For only specific backports:
require 'backports/1.9.1/kernel/require_relative'
require 'backports/2.0.0/enumerable/lazy'

# For all backports up to a given version
require 'backports/1.9.2' # All backports for Ruby 1.9.2 and below

Note: about a dozen of backports have a dependency that will be also loaded. For example, the backport of Enumerable#flat_map uses flatten(1), so if required from Ruby 1.8.6 (where Array#flatten does not accept an argument), the backport for Ruby's 1.8.7 flatten with an argument will also be loaded.

With bundler, add to your Gemfile:

gem 'backports', :require => false

Run bundle install and require the desired backports. Compatible with Ruby itself, JRuby and Rubinius.

Complete List of backports

Ruby 2.5 backports

  • Array

    • append, prepend

  • Dir

    • children, each_child

  • Enumerable

    • any?, all?, none?, one? (with pattern argument)

  • Hash

    • slice

    • transform_keys

  • Integer

    • sqrt

    • allbits?, anybits? and nobits?

  • Kernel

    • yield_self

  • Module

    • attr, attr_accessor, attr_reader, attr_writer (now public)

    • define_method, alias_method, undef_method, remove_method (now public)

  • String

    • delete_prefix, delete_prefix!

    • delete_suffix, delete_suffix!

  • Struct

    • new (with keyword_init: true)

Ruby 2.4 backports

  • Comparable

    • clamp

  • Enumerable

    • sum

    • uniq

  • Hash

    • compact, compact!

    • transform_values, transform_values!

  • Regexp

    • match?

  • String

    • match?

  • FalseClass, Fixnum, Float, NilClass, TrueClass

    • dup

Ruby 2.3 backports

  • Array

    • bsearch_index

    • dig

  • Enumerable

    • chunk_while

    • grep_v

  • Hash

    • dig

    • fetch_values

    • to_proc

    • <=, <, >=, >

  • Numeric

    • negative?

    • positive?

  • String

    • unary + and -

  • Struct

    • dig

Ruby 2.2 backports

  • Enumerable

    • slice_after

    • slice_when

  • Float

    • prev_float

    • next_float

  • Kernel

    • itself

  • Method

    • curry

    • super_method

  • String

    • unicode_normalize

    • unicode_normalize!

    • unicode_normalize?

Ruby 2.1 backports

  • Array

    • to_h

  • Bignum

    • bit_length

  • Enumerable

    • to_h

  • Fixnum

    • bit_length

  • Module

    • include (now public)

Ruby 2.0 backports

  • Array

    • bsearch

  • Enumerable

    • lazy

  • Enumerator::Lazy

    • all methods

  • Hash

    • default_proc= (with nil argument)

    • to_h

  • nil.to_h

  • Range

    • bsearch

  • Struct

    • to_h

Ruby 1.9.3 backports

  • File

    • NULL

  • IO

    • advise (acts as a noop)

    • write, binwrite

  • String

    • byteslice

    • prepend

Ruby 1.9.2 backports

  • Array

    • rotate, rotate!

    • keep_if, select!

    • product (with block)

    • repeated_combination, repeated_permutation

    • sort_by!

    • uniq, uniq! (with block)

  • Complex

    • to_r

  • Dir

    • home

  • Enumerable

    • chunk

    • flat_map, collect_concat

    • join

    • slice_before

  • Float::INFINITY, NAN

  • Hash

    • keep_if, select!

  • Object

    • singleton_class

  • Random (new class)

Note: The methods of Random can't be required individually; the class can only be required whole with require 'backports/1.9.2/random'.

Ruby 1.9.1 backports

Additionally, the following Ruby 1.9 features have been backported:

  • Array

    • try_convert

    • sample

  • Enumerable

    • each_with_object

    • each_with_index (with arguments)

  • Enumerator

    • new (with block)

  • File

    • binread

    • to_path

    • All class methods accepting filenames will accept files or anything with a #to_path method.

    • accepts an options hash.

  • Float

    • round

  • Hash

    • assoc, rassoc

    • key

    • try_convert

    • default_proc=

  • Integer

    • magnitude

    • round

  • IO

    • bin_read

    • try_convert

    • ungetbyte

    • accepts an options hash.

  • Kernel

    • require_relative

  • Math

    • log (with base)

    • log2

  • Numeric

    • round

  • Object

    • define_singleton_method

    • public_method

    • public_send

  • Proc

    • yield

    • lambda?

    • curry

    • ===

  • Range

    • cover?

  • Regexp

    • try_convert

  • String

    • ascii_only?

    • chr

    • clear

    • codepoints, each_codepoint

    • get_byte, set_byte

    • ord

    • try_convert

Enumerator can be accessed directly (instead of Enumerable::Enumerator)

To include only these backports and those of the 1.8 line, require "backports/1.9.1".

Moreover, a pretty good imitation of BasicObject is available, but since it is only an imitation, it must be required explicitly:

require 'backports/basic_object'

Ruby 1.8.7

Complete Ruby 1.8.7 backporting (core language). Refer to the official list of changes. That's about 130 backports!

Only exceptions:

  • String#gsub (the form returning an enumerator)

  • GC.stress= (not implemented)

  • Array#choice (removed in 1.9, use 1.9.1's Array#sample instead)


Libraries are slowly being backported. You simply require them as usual after requiring 'backports/std_lib'. Requiring 'backports/std_lib' after the standard libraries is also supported.

require "backports/std_lib"
require "prime" # => false, even in Ruby 1.8.x

The following libraries are up to date with Ruby 1.9.3:

  • Matrix

  • Prime

  • Set

The following library is to date with Ruby 2.0.0:

  • OpenStruct (ostruct)

I am aware of the following backport gem, which probably won't make it into this gem:

Requiring backports for a given version of Ruby will also load 'backports/std_lib'.

Forcing incompatibilities

Some backports would create incompatibilities in their current Ruby version but could be useful in some projects. It is possible to request such incompatible changes. Backports currently supports the following:

  • Hash

    • select (returns a Hash instead of an Array)

  • Enumerable / Array

    • map (returns an enumerator when called without a block)

  • String

    • length, size (for UTF-8 support)

These must be imported in addition to the backports gem, for example:

require "backports/force/hash_select"
{}.select{} # => {}, even in Ruby 1.8


Thanks for the bug reports and patches, in particular the repeat offenders:

  • Arto Bendiken ( bendiken )

  • Konstantin Haase ( rkh)

  • Roger Pack ( rdp )

The best way to submit a patch is to also submit a patch to ruby/spec and then a patch to backports that make it pass the spec. To test rubyspec:

git submodule init && git submodule update # => pulls rubyspecs
rake spec[array/bsearch]       # => tests Array#bsearch
rake spec[array/*]             # => tests all backported Array methods
rake spec  (or rake spec[*/*]) # => all rubyspecs for backported methods

Failures that are acceptable are added the to `tags` file.


backports is released under the terms of the MIT License, see the included LICENSE file.


Marc-André Lafortune