patternie draft

lib/patternie.rb

@@ -0,0 +1,86 @@
+require 'rubygems'
+require 'active_support'
+require 'rails'
+
+class Accumulator
+  def initialize(acc)
+    @acc = acc
+  end
+  def method_missing(sym, *args)
+    @acc << sym
+  end
+end
+
+module Estudante
+  def self.acc
+    @@acc ||= []
+  end
+
+  def self.case_fields(&block)
+    Accumulator.new(acc).instance_eval &block
+  end
+
+  case_fields {turma}
+end
+
+class AlunoUniversitario
+  include Estudante
+
+  attr_reader :turma
+  def initialize(turma)
+    @turma = turma
+  end
+
+end
+class ProcMatcher
+
+  def matches?(p, obj)
+    @obj = obj
+    self.instance_eval &p
+  end
+
+  def method_missing(method, *args)
+    if @obj.kind_of?(method.to_s.constantize)
+      field = method.to_s.constantize.acc[0]
+      required_value = args[0] # 55
+      @obj.send(field)==required_value
+    else
+      false
+    end
+  end
+
+end
+class PatternMatcher
+  def initialize(pattern)
+    @pattern = pattern
+  end
+  def matches?(*args)
+    is_same_type = (@pattern.kind_of?(Class) && args[0].kind_of?(@pattern))
+    is_equal = @pattern==args[0]
+    is_proc_matches = (@pattern.kind_of?(Proc) && ProcMatcher.new.matches?(@pattern,args[0]))
+    is_same_type || is_equal || is_proc_matches
+  end
+end
+
+class Fa
+
+  @@acc = []
+  def self.f(*args, &block)
+    if block_given?
+      @@acc << [PatternMatcher.new(args[0]), block]
+    else
+      found = @@acc.find { |el| el[0].matches?(*args) }
+      found[1].call(*args) if found
+    end
+  end
+
+  f(1) { 15 }
+  f(Integer) {13}
+  f(proc {Estudante(30)}) { "uhu! achei universitario!" }
+  f(proc {Estudante(35, turma)}) {"Pq 35 eh o que ha!" }
+
+  puts f(1)
+  puts f(22222)
+  puts f(AlunoUniversitario.new(30))
+  puts f(AlunoUniversitario.new(35))
+end