turn off let floating

Bernard James POPE bjpop at cs.mu.OZ.AU
Wed Apr 21 12:02:32 EDT 2004

Hi Andre,

> There's another way which you missed: using implicit parameters.  I 
> remember reading a paper a while ago called Global Variables in Haskell 
> (sorry, don't remember the author -- Jones, perhaps?) which did similar 
> benchmarking to yours, and carrying around the global variable with an 
> implicit parameter was faster than using a global mutable counter via 
> "unsafePerformIO $ newIORef ...".

Thanks for the note. That was in the paper by John Hughes. The
performance difference between unsafePerformIO and implicit parameters
is not significant in his test case. I think he was surprised that 
implicit parameters worked so well (I am too). 

That doesn't mean I should rule it out completely. I'll have a look into

Also, implicit parameters are less convenient for the program transformation
that I use in buddha, whereas a truly global variable is ideal.

On the other hand the FFI approach looks a lot faster already, and Simon
has suggested that I can inline unsafePerformIO.


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