Either handles Just and Nothing as Success and Failure

README.md

@@ -90,9 +90,10 @@ Maybe(1).to_s             == '1'
 ```
 
 `#or`
-Maybe(nil).or(1)          == 1
-Maybe(1).or(2)            == 1
-Maybe(nil).or(nil)        == Just(nil)
+Maybe(nil).or(1)          == Just(1)
+Maybe(1).or(2)            == Just(1)
+Maybe(nil).or(1)          == Just(1)
+Maybe(nil).or(nil)        == Nothing
 
 Falsey values (kind-of) examples:
 

lib/monadic/either.rb

@@ -8,7 +8,9 @@ def self.chain(initial=nil, &block)
 
     def self.unit(value)
       return value if value.is_a? Either
-      return Failure.new(value) if value.nil? || (value.respond_to?(:empty?) && value.empty?) || !value
+      return Nothing                  if value.is_a? Nothing
+      return Success.new(value.fetch) if value.is_a? Just
+      return Failure.new(value)       if value.nil? || (value.respond_to?(:empty?) && value.empty?) || !value
       return Success.new(value)
     end
 

spec/either_spec.rb

@@ -39,6 +39,10 @@
     Failure(1).should_not == Failure(2)
   end
 
+  it 'Either(Nothing) is a Failure' do
+    Either(Nothing).should == Failure(Nothing)
+  end
+
   it 'wraps a nil result to Failure' do
     Success(nil).bind { nil }.should == Failure(nil)
   end
@@ -241,6 +245,14 @@ def process_content(content); content.start_with?('b') ? Success(content.upcase)
     either.fetch.should be_a KeyError
   end
 
+  it 'Either(Nothing) returns a Failure' do
+    Either(Nothing).should == Failure(Nothing)
+  end
+
+  it 'Either(Just) returns a Success' do
+    Either(Just.new(1)).should == Success(1)
+  end
+
   it 'instance variables' do
     result = Either.chain do
       bind { @map = { one: 1, two: 2 } }