local w=-1 local G=1 local y=0
-- /**
--  * The data structure representing a diff is an array of tuples:
--  * [[DIFF_DELETE, 'Hello'], [DIFF_INSERT, 'Goodbye'], [DIFF_EQUAL, ' world.']]
--  * which means: delete 'Hello', add 'Goodbye' and keep ' world.'
--  */
local DIFF_DELETE = -1
local DIFF_INSERT = 1
local DIFF_EQUAL = 0
