class String
	# reformats a list (newline separated) into columns
	def columnize(columns=2, orientation="vertical", prepend="")
		list		= self.split("\n")
		sizes		= []
		out			= ""
		items		= (list.length.to_f/columns.to_f).ceil #items per column
		orientation	= (orientation[0,1].downcase == "v")
		if (orientation) then
			0.upto(columns-1) { |col|
				0.upto(items-1) { |row|
					item		= col*items+row
					list[item]	= list[item].nil? ? "" : prepend+list[item]
					sizes[col]	= [sizes[col], list[item].length].max
				}
			}
			0.upto(items-1) { |row|
				0.upto(columns-1) { |col|
					item		= col*items+row
					out			= out+list[item]+" "*(((sizes[col]-list[item].length)+2))
				}
				out	= out+"\n"
			}
		else
			0.upto(columns-1) { |col|
				0.upto(items-1) { |row|
					item		= row*columns+col
					list[item]	= list[item].nil? ? "" : prepend+list[item]
					sizes[col]	= [sizes[col], list[item].length].max
				}
			}
			0.upto(items-1) { |row|
				0.upto(columns-1) { |col|
					item		= row*columns+col
					out			= out+list[item]+" "*(((sizes[col]-list[item].length)+2))
				}
				out	= out+"\n"
			}
		end
		return out[0..-2]
	end
end