Hi, I have a nice big data structure that I serialise to a file using "show", and read back in using "read". This data structure has deriving (Read, Show), which makes it all nice and easy to save and load this data structure, without worrying about parsing code etc. The problem is that this data structure can become quite big, and while show operates lazily, read does not. I understand the reason for this - that it internally calls reads and that on a parse error reads will not return a result - i.e. it has to get to the end to determine whether the parse was valid or not. However, in my particular case, I know the data structure is valid, and if it isn't then I'm quite happy with the parser throwing an error half way through - after having lazily returned half of the data. A short example, which shows up the exact same issue is: head ((read $ show [1..n]) :: [Int]) The time of this operation is dependant on n, because of the strictness of read. What is the best way to modify the code to have read operate lazily? Is there any method that doesn't require writing a custom parser? Is there any standard way for solving a problem like this? Thanks Neil