= PatternMatching module


== What

Provides a pure ruby module that:
* can build structured objects easily
* can enable pattern match of objects
* can define method as a partial function style

== Installing

sudo gem install patternmatching

== The basics

This module provides methods for tree pattern matching features.

* For detail, see Pattern matching[http://en.wikipedia.org/wiki/Pattern_matching]
* Syntax based on meta-programming, like "rspec", and so on.

Note: Default equivalence used in structured pattern matching is
based on "pattern === data",
so "foo(Numeric)" matches "foo(100)".

From ver. 0.2.0, thread unsafeness restriction is removed.

== Demonstration of usage

Symbols(e.g. ":a", ":right_value")
in patterns is passed as variable
to the following block when the pattern matched.

=== Pattern matching expression
# If installed from gem
# require "rubygems"
# gem "patternmatching"
require "patternmatching"

# For DSL style code, include PatternMatching
include PatternMatching

# match example
def calc(code)
make(code) seems as {plus(:a, :b) do calc(a) + calc(b) end
seems as :b) do calc(a) * calc(b) end
seems something do code end
}
end

code = build 100), 200)
p calc(code) #=> 10200

=== Partial style method

require "patternmatching"

# Structured data builder
code = PatternMatching.build 100), 200)

# Partial style method example
class Calc
# At first, extends with the module
extend PatternMatching

# def calcm(o), as 3 partial styles
func(:calcm).seems as :b) do
calcm(b) + calcm(b)
end
func(:calcm).seems as :b) do
calcm(a) * calcm(b)
end
func(:calcm).seems as :value do
value
end
end

# use as standard method
p Calc.new.calcm(code) #=> 10200

=== Array/Enumerable pattern

require "patternmatching"

include PatternMatching

# Example for matching Enumerable
is = build { exact([1,2,3,4,5]) }
make is do
# _! matches rest of lists
seems as _!(:c)]) do
puts a.to_s + ", " + b.to_s + " and " + c.to_s
end
seems something do
puts "not matched"
end
end # => "1, 2, and 345"

=== Hash pattern

require "patternmatching"

include PatternMatching

# Example for matching Hash
dict = build { => "Taro", :age => 5 }
make dict do
seems as => :name} do
puts "He is " + name
end
seems something do
puts "no name"
end
end # => "He is Taro"

=== Non-Hash/Object pattern

require "patternmatching"

include PatternMatching

class Person
def initialize(name, age)
@name = name
@age = age
end
attr :name
attr :age
end

# Example for matching Object except Hash
person = Person.new("Jiro", 3)
make person do
seems as => :name} do
puts "He is " + name
end
seems something do
puts "no name"
end
end # => "He is Jiro"

=== Field Access Example
It is ver. 0.2.0 API

require "patternmatching"

include PatternMatching

class Foo
def initialize
@name = "Foo"
end
attr :name
def foo
end

def bar
make "bar" do
seems as :val do
foo
# To access fields like this.name or this.name = ...
the.name = val
# To access self as this
this
end
end
end

func(:buzz).seems as :val do
the.name = val
this
end
end

o = Foo.new
p o.bar == o #=> true
p o.name #=> "bar"
p o.buzz("buzz") == o #=> true
p o.name #=> "buzz"

=== Pattern with Condition Example
It is from ver. 0.2.2 API

require "patternmatching"

include PatternMatching

num = 100
result = make num do
seems as :n, with < 10 do
true
end
seems as :n, with >= 10 do
false
end
end

p result #=> false

== Forum

Visit the project forum in RubyForge.

== How to submit patches

Read the steps for fixing other people's code[http://drnicwilliams.com/2007/06/01/8-steps-for-fixing-other-peoples-code/] and for section Submit patch to Google Groups[http://drnicwilliams.com/2007/06/01/8-steps-for-fixing-other-peoples-code/#8b-google-groups], use the forum above.

The trunk repository is
svn://rubyforge.org/var/svn/patternmatching/trunk
for anonymous access.

== License

This code is free to use under the terms of the MIT license.

== Links

* Site[http://patternmatching.rubyforge.org/]
* Page[http://rubyforge.org/projects/patternmatching/]
* Doc[http://patternmatching.rubyforge.org/rdoc/]

== Contact

Comments are welcome. Send a message to the forum.

== Authors

* ICHIYAMA Ryoichi: bellbind at gmail dot com

blog[http://d.hatena.ne.jp/bellbind/] (written in Japanese)
could be help you.