Functional Ruby

A gem for adding Erlang, Clojure, and Go inspired functional programming tools to Ruby.

NOTE: As of version 0.7.0 the concurrency tools from this gem have been moved to the concurrent-ruby gem.

The project is hosted on the following sites:

Introduction

Two things I love are Ruby and functional programming. Sadly, the former is generally not associated with the latter. Unfortunately, too many people are blinded by their belief that Ruby is an object-oriented language. I reject this assertion. Ruby is certainly object-based, since everything is an object, but entire large-scale programs can be built without ever defining a single class. But Ruby's features that support functional programming don't stop there.

Ask ten different programmers to define the term "functional programming" and you will likely get ten different answers. One characteristic that will certainly be on all their lists is support for higher order functions. Put simply, a higher order function is any function that can take one or more functions as parameters and/or return a function as a result. Many functional languages, such as Erlang, Haskell, and Closure, support higher order functions. Higher order functions are a remarkable tool that can completely change the was software is designed. Most classicaly object-oriented languages do not support higher order functions. Unfortunately, Ruby does not directly support higher order functions. Thanksfully, Ruby does give us blocks, procs, and lambdas. Though not strictly higher order functions, in most cases they are functionally equivalent.

If you combine Ruby's ability to create functions sans-classes with the power of blocks/procs/lambdas, Ruby code can follow just about every modern functional programming design paradigm. Hence, I consider Ruby to be a multi-paradigm language. Add to this Ruby's vast metaprogramming capabilities and Ruby is easily one of the most powerful languages in common use today.

This gem is my small and humble attempt to help Ruby reach its full potential as a highly performant, functional programming language. Virtually every function in this library takes a block parameter. Some allow a block plus one or more proc arguments. Most operate on data structures rather than being buried in data structures. Finally, several of the tools in this library are Ruby implementations of some of my favorite features from other functional programming languages. Not every function is pure, but functions with side effects are easy to spot because they almost always have names that end in an exclamation point.

My hope is that this gem will help Ruby programmers explore Ruby as a functional language and improve their code in ways our object oriented brethern never dreamed possible.

Goals

My goal is to implement various functional programming patterns in Ruby. Specifically:

Stay true to the spirit of the languages providing inspiration
But implement in a way that makes sense for Ruby
Keep the semantics as idiomatic Ruby as possible
Support features that make sense in Ruby
Exclude features that don't make sense in Ruby
Keep everything small
Be as fast as reasonably possible

Features (and Documentation)

Several features from Erlang, Go, and Clojure have been implemented thus far:

Interface specifications with Erlang-style Behavior
A Catalog class for managing sets of key/value pairs in a manner similar to Erlang's proplists
A toolkit of collection utilities for operating on list-like data structures
A set of string inflections borrowed from Active Support
Function overloading with Erlang-style Pattern Matching
Tools for introspecting the runtime Platform for information about the operating system and Ruby version
Search and sort algorithms like you remember from your algorithms class, but with a functional twist
Several useful functional Utilities

Is it any good?

Yes

Supported Ruby versions

MRI 1.9.2, 1.9.3, 2.0, 2.1, and JRuby (1.9 mode). This library is pure Ruby and has no gem dependencies. It should be fully compatible with any Ruby interpreter that is 1.9.x compliant.

Install

gem install functional-ruby

or add the following line to Gemfile:

gem 'functional-ruby'

and run bundle install from your shell.

Once you've installed the gem you must require it in your project:

require 'functional'

Examples

For complete examples, see the specific documentation linked above. Below are a few examples to whet your appetite.

Pattern Matching (Erlang)

Documentation: Pattern Matching

require 'functional/pattern_matching'

class Foo
  include PatternMatching

  defn(:greet, :male) {
    puts "Hello, sir!"
  }

  defn(:greet, :female) {
    puts "Hello, ma'am!"
  }
end

foo = Foo.new
foo.greet(:male)   #=> "Hello, sir!"
foo.greet(:female) #=> "Hello, ma'am!"

Behavior (Erlang)

Documentation: Behavior

require 'functional/behavior'

behaviour_info(:gen_foo, foo: 0, self_bar: 1)

class Foo
  behavior(:gen_foo)

  def foo
    return 'foo/0'
  end

  def self.bar(one, &block)
    return 'bar/1'
  end
end

foo = Foo.new

Foo.behaves_as? :gen_foo    #=> true
foo.behaves_as?(:gen_foo)   #=> true
foo.behaves_as?(:bogus)     #=> false
'foo'.behaves_as? :gen_foo  #=> false

Utilities

Documentation: Utilities

Infinity #=> Infinity
NaN #=> NaN

repl? #=> true when called under irb, pry, bundle console, or rails console

safe(1, 2){|a, b| a + b} #=> 3
safe{ eval 'puts "Hello World!"' } #=> SecurityError: Insecure operation

pp_s [1,2,3,4] #=> "[1, 2, 3, 4]\n" props to Rha7

delta(-1, 1) #=> 2
delta({count: -1}, {count: 1}){|item| item[:count]} #=> 2

# And many more!

Copyright

License

Released under the MIT license.

http://www.opensource.org/licenses/mit-license.php

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.