> Mike, common subsequence sharing really makes a big 
> difference. For example list sharing is one of the major 
> assumptions in estimating the time complexity of the algorithms in
> 

Thanks for the advice, it's certainly one of the things I will put on my
list of future opportunities. I can't immediately see how to combine it
with lazy evaluation, but I'll stew on it for a while.

I've recently extended the optimizations I do in two particular areas -
compile-time moving of sub-expressions out of loops, and run-time lazy
evaluation, and between them they have made a big difference to
execution time for some complex stylesheets. The bad news is that most
stylesheets are not complex enough to benefit from them!

Michael Kay
Software AG
home: Michael.H.Kay@xxxxxxxxxxxx
work: Michael.Kay@xxxxxxxxxxxxxx 



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