Re: PCODE Interpereters 101

On 3 Feb 1999 23:51:59 -0500, Tom Lane <tgl@netcom.com> wrote:
>Now maybe the programming styles I'm used to are hopelessly
>troglodyte, but I've seen darn few programs other than
>recursive-descent compilers that even *have* two-level-nested
>procedures, much less programs in which such procedures' access to
>their grandparents' locals are so frequent as to be worth improving at
>the cost of a slowdown in all procedure calls.


Some languages (e.g., Common Lisp, Scheme, etc.) bind the execution
environment at compile time. This environment may be arbitrarily
nested. For reasonable performance, such languages have to have fast
access to non-locals.


>I think the only reason display-style implementations were ever
>popular at all is that Wirth's Pascal book described doing it that
>way; for most practical purposes static link is superior.


Many mainframe processor designs have displays maintained by hardware
to some fixed depth. Compilers for such machines frequently limit
function nesting depth to the maximum allowed by the hardware.




George Neuner
Dynamic Resolutions, Inc.

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