List#infold_up and List#infold_down

lib/list_class.rb

@@ -128,13 +128,41 @@ def to_s
         size < @@result_size_limit ? List.new(results) : Error.new("OVERSIZE")
       end
     end
-
-
+
+
+    duck_handle :infold_down do
+      @contents.reverse.inject do |memo, item|
+        case
+          when memo.nil?
+            item
+          when memo.kind_of?(Array)
+            memo.collect {|branch| item.grab(branch)}.flatten.compact
+          else
+            item.grab(memo)
+          end
+      end
+    end
+
+
+    duck_handle :infold_up do
+      @contents.inject do |memo, item|
+        case
+          when memo.nil?
+            item
+          when memo.kind_of?(Array)
+            memo.collect {|branch| item.grab(branch)}.flatten.compact
+          else
+            item.grab(memo)
+          end
+      end
+    end
+
+
     duck_handle :length do
       Int.new(@contents.length)
     end
-
-
+    
+    
     duck_handle :map do
       Closure.new(["be"],"map(#{self.inspect}, ?)") do |item|
         new_contents = @contents.collect {|i| i.deep_copy}

spec/lists/messages/infold_down_message_spec.rb

@@ -0,0 +1,48 @@
+#encoding: utf-8
+require_relative '../../spec_helper'
+
+describe "List" do
+  describe "the :infold_down message for Lists" do
+    it "should be something Lists recognize" do
+      List.recognized_messages.should include(:infold_down)
+    end
+
+    it "should produce the result of each item BEING GRABBED BY the next from RIGHT to LEFT" do
+      bunch = list([int(2), int(3), int(4)])
+      bunch.infold_down.should be_a_kind_of(Int)
+      bunch.infold_down.inspect.should == "2"
+    end
+
+    it "should work for empty Lists, returning nil" do
+      list.infold_down.should == nil
+    end
+
+    it "should do all the grabbing stuff" do
+      do_math_later = list( [message("+"), message("neg"), int(2)] )
+      interpreter(contents:[do_math_later]).inspect.should == "[(:+, :neg, 2) :: :: «»]"
+      interpreter(contents:[do_math_later], script:"infold_down").run.inspect.should == 
+        "[λ(-2 + ?,[\"neg\"]) :: :: «»]"
+    end
+
+    it "should work even when things don't technically #grab one another, since that's how grab works" do
+      interpreter(contents:[list([int(9)]*7)], script:"infold_down").run.inspect.should == "[9 :: :: «»]"
+    end
+
+    it "should work when an intermediate result returns an Array" do
+      cause_havoc = list([
+        message("shatter"),
+        list( [message("*"), message("foo"),message("trunc")] )
+        ])
+      interpreter(contents:[cause_havoc]).inspect.should == "[(:shatter, (:*, :foo, :trunc)) :: :: «»]"
+      interpreter(contents:[cause_havoc], script:"infold_down").run.inspect.should == 
+        "[:*, :foo, :trunc :: :: «»]"
+    end
+
+    it "should work when an intermediate result returns nil" do
+      cause_havoc = list( [message("zap"), message("foo"), int(4)])
+      interpreter(contents:[cause_havoc]).inspect.should == "[(:zap, :foo, 4) :: :: «»]"
+      interpreter(contents:[cause_havoc], script:"infold_down").run.inspect.should == "[:: :: «»]"
+    end
+
+  end
+end

spec/lists/messages/infold_up_message_spec.rb

@@ -0,0 +1,49 @@
+#encoding: utf-8
+require_relative '../../spec_helper'
+
+describe "List" do
+  describe "the :infold_up message for Lists" do
+    it "should be something Lists recognize" do
+      List.recognized_messages.should include(:infold_up)
+    end
+
+    it "should produce the result of each item BEING GRABBED BY the next from RIGHT to LEFT" do
+      bunch = list([int(2), int(3), int(4)])
+      bunch.infold_up.should be_a_kind_of(Int)
+      bunch.infold_up.inspect.should == "4"
+    end
+
+    it "should work for empty Lists, returning nil" do
+      list.infold_up.should == nil
+    end
+
+    it "should do all the grabbing stuff" do
+      do_math_later = list( [int(2), message("+") ] )
+      interpreter(contents:[do_math_later]).inspect.should == "[(2, :+) :: :: «»]"
+      interpreter(contents:[do_math_later], script:"infold_up").run.inspect.should == 
+        "[λ(2 + ?,[\"neg\"]) :: :: «»]"
+    end
+
+    it "should work even when things don't technically #grab one another, since that's how grab works" do
+      interpreter(contents:[list([int(9)]*7)], script:"infold_up").run.inspect.should == "[9 :: :: «»]"
+    end
+
+    it "should work when an intermediate result returns an Array" do
+      cause_havoc = list([
+        list( [message("*"), int(99), message("trunc")] ),
+        message("shatter"),
+        message("neg")]
+        )
+      interpreter(contents:[cause_havoc]).inspect.should == "[((:*, 99, :trunc), :shatter, :neg) :: :: «»]"
+      interpreter(contents:[cause_havoc], script:"infold_up").run.inspect.should == 
+        "[-99 :: :: «»]"
+    end
+
+    it "should work when an intermediate result returns nil" do
+      cause_havoc = list( [ message("foo"), message("zap"), int(4)])
+      interpreter(contents:[cause_havoc]).inspect.should == "[(:foo, :zap, 4) :: :: «»]"
+      interpreter(contents:[cause_havoc], script:"infold_up").run.inspect.should == "[4 :: :: «»]"
+    end
+
+  end
+end