Set default value for Reline.input, Reline.output and Reline.special_…

…prefixes

lib/reline.rb

@@ -114,7 +114,11 @@ def filename_quote_characters=(v)
     end
 
     def special_prefixes=(v)
-      @special_prefixes = v.encode(encoding)
+      if v.nil?
+        @special_prefixes = ''
+      else
+        @special_prefixes = v.encode(encoding)
+      end
     end
 
     def completion_case_fold=(v)
@@ -174,14 +178,25 @@ def dialog_proc(name_sym)
     end
 
     def input=(val)
-      raise TypeError unless val.respond_to?(:getc) or val.nil?
-      if val.respond_to?(:getc) && io_gate.respond_to?(:input=)
-        io_gate.input = val
+      if val.nil?
+        io_gate.input = STDIN
+        return
+      elsif !val.respond_to?(:getc)
+        raise TypeError
       end
+
+      io_gate.input = val
     end
 
     def output=(val)
-      raise TypeError unless val.respond_to?(:write) or val.nil?
+      if val.nil?
+        @output = STDOUT
+        io_gate.output = STDOUT
+        return
+      elsif !val.respond_to?(:write)
+        raise TypeError
+      end
+
       @output = val
       io_gate.output = val
     end