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[Caml-list] Evaluation Order
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David McClain
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Brian Rogoff
- David McClain
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John Max Skaller
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Brian Rogoff
- Dave Mason
- John Max Skaller
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Brian Rogoff
- John Max Skaller
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Brian Rogoff
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| Date: | -- (:) |
| From: | John Max Skaller <skaller@o...> |
| Subject: | Re: [Caml-list] Evaluation Order |
Brian Rogoff wrote: > > Perhaps binding record fields left to right makes sense, > > And tuples, and (::), and ... > > Why not make the default correspond to everyone's intuition? It may clobber performance, and, it isn't all that obvious anyhow. Here is the 'classic' example from C: x[i++] = y[i++] [If you think you know the answer .. just consider that i might alias x :-] If the order of evaluation is strictly specified, a lot of results must be written to memory prematurely. It is one reason why C is slower than Fortran. I suspect it is processor dependent. C specifies sequence points: places where write operations must be completed before continuing. If you do a read before that, the result is indeterminate. The rules try to make efficient 'in register' operations possible and allow enough flexibility to reorder instructions to suit a processors caching and pipelining model -- while still making common idioms work. I'm no expert. I simply advise caution here. _Functional_ expressions can be optimised in useful ways at very low processor dependent levels. Lets not stop the Ocaml team trying to beat both C _and_ Fortran! -- John (Max) Skaller, mailto:skaller@maxtal.com.au 10/1 Toxteth Rd Glebe NSW 2037 Australia voice: 61-2-9660-0850 checkout Vyper http://Vyper.sourceforge.net download Interscript http://Interscript.sourceforge.net ------------------- Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr