copied list code from risc instructions

lib/common/list.rb

@@ -0,0 +1,55 @@
+module Common
+  module List
+
+    # set the next instruction (also aliased as <<)
+    # throw an error if that is set, use insert for that use case
+    # return the instruction, so chaining works as one wants (not backwards)
+    def set_next nekst
+      raise "Next already set #{@next}" if @next
+      @next = nekst
+      nekst
+    end
+    alias :<< :set_next
+
+    # during translation we replace one by one
+    def replace_next nekst
+      old = @next
+      @next = nekst
+      @next.append old.next if old
+    end
+
+    # get the next instruction (without arg given )
+    # when given an interger, advance along the line that many time and return.
+    def next( amount = 1)
+      (amount == 1) ? @next : @next.next(amount-1)
+    end
+
+    # set the give instruction as the next, while moving any existing
+    # instruction along to the given ones's next.
+    # ie insert into the linked list that the instructions form
+    def insert instruction
+      instruction.set_next @next
+      @next = instruction
+    end
+
+    # return last set instruction. ie follow the linked list until it stops
+    def last
+      code = self
+      code = code.next while( code.next )
+      return code
+    end
+
+    # set next for the last (see last)
+    # so append the given code to the linked list at the end
+    def append code
+      last.set_next code
+    end
+
+    def length labels = []
+      ret = 1
+      ret += self.next.length( labels ) if self.next
+      ret
+    end
+
+  end
+end