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Re: compile-time taint checking and the halting problem

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Dan Sugalski
October 23, 2000 10:23
Re: compile-time taint checking and the halting problem
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At 09:44 AM 10/23/00 -0700, Larry Wall wrote:
>David L. Nicol writes:
>: Steve Fink wrote (and I edited slightly):
>: > <groan>  I can't figure out why so many people misinterpret my RFC12
>: > as requiring a solution to the halting problem.
>: a large class of incompletely expressed
>: suggestions appear to get grouped into
>: "This requires solving the halting problem!"
>: without providing further explanation.
>Well, in my case, I wasn't actually meaning it strictly.  Sorry for the
>imprecision--it's hard to squeeze everything into a talk.  To me the
>saying is just shorthand for "potentially sufficiently computationally
>expensive that I don't want to worry about it for the default case".
>In other words, I was lumping polynomial in with exponential, and RFC12
>feels polynomial to me.  And it's not that I'm against the availability
>of polynomial algorithms in the parser, or the use of polynomial
>algorithms in general--I just think the default compile-and-run parser
>should avoid them.

I'm really hoping to make allowances for a variety of optional 
optimizations. We can save the nastier things (and with perl's active data, 
a lot of stuff could reasonably be classed as difficult--good 
optimization's going to need fairly complex flow analysis, I think) for 
explicit requests, possibly with different default optimization levels for 
parse-and-go perl and compile-to-bytecode perl.


--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai                         have teddy bears and even
                                      teddy bears get drunk

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