Hi Kartik, No it can't be simplified to that, though the reason is a little subtle. Firstly we have to remember that every heap node follows the same structure: first we have the node header, then we have pointers to arguments. Consider: HEAP_CVAL show HEAP_INT 42 PUSH_HEAP HEAP_CVAL putStrLn HEAP_OFF_N1 ... RETURN_EVAL This builds in the heap Int 42 stored somewhere else ^ +--------+----|----+--------------+-----------+ | show | | | putStrLn | | +--------+---------+--------------+-----|-----+ ^ | +------------------------------------+ However: PUSH_HEAP HEAP_CVAL putStrLn HEAP_CVAL show HEAP_INT 42 RETURN_EVAL builds Int 42 ^ +-------------+----------+-----|------+ | putStrLn | show | | | +-------------+----------+------------+ So in the first case we get a an application to putStrLn with it's argument pointer pointing to an application of show. In the second case we get an application to putStrLn with it's argument pointer being the header of show (i.e. a random junk pointer). Of course we could have something like PUSH_HEAP HEAP_CVAL putStrLn HEAP_PTR_CVAL show HEAP_INT 42 RETURN_EVAL where HEAP_PTR_CVAL inserts a pointer to the next item and then writes that item with a CVAL. Giving +-------------+-----------+----------+------------+ | putStrLn | | show | ... | +-------------+----|------+----------+------------+ | ^ +-----------+ But that only works for functions with one argument, so in general you either end up needing heap offsets (nhc's solution) or a stack (yhc's solution). Hope that explains it :-) Thanks Tom Kartik Vaddadi wrote:

Hello, I'm a newbie at yhc & nhc, and I wonder: The nhc bytecode that Tom Shackell's presentation gives -- can't it be simplified by eliminating the HEAP_OFF_N1 and placing 'putStrLn' before 'show' in the heap, like this:

PUSH_HEAP HEAP_CVAL putStrLn HEAP_CVAL show HEAP_INT 42 RETURN_EVAL

Is there some fundamental reason why nhc can't generate such code (which yhc does not suffer from) or is this just an artefact of the current implementation? Thanks, and sorry if the question was dumb.