Article View: comp.lang.misc
Article #5264Re: Var scoping in Wirth-type languages
From: Erland Sommarskog
Date: Fri, 11 Mar 1988 21:22
Date: Fri, 11 Mar 1988 21:22
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00704a-Liber,N.J. (nevin1@ihlpf.UUCP) writes:
>Globals, unless implemented with the optimization I'm going to state later,
>are much less efficient than using locals! If I didn't make that point
>clear in my last posting, please excuse me.
>
>For every level deep that a variable is used after it is declared, one
>climb up the static chain of activation records (I think this is the right
Nevin continues with an example, which I have deleted.
Yes, that kind of globals are slower, for sure. I was thinking of
variables declared on module/program level. They are allocated to a
fix adress, and there very quick to access. In the case I quoted, I
think they were global on process level. I don't know the details of
the implementation, but it seems likely that time to access a process
variable and local variable are about the same.
>In addition to the standard var declarations, one should be allowed to
>declare a variable 'static' (to steal from C). The scoping would be the
>...
>Note: This optimization can already be done on variables that can be
>determined not to be used recursively and are referenced at a level deeper
>then they are declared. However, by adding explicit static declarations,
>the programmer has much more flexibility. Comments??
It seems to me that compiler should have the headache to decide which
variables should be static, not the programmer.
--
Erland Sommarskog
ENEA Data, Stockholm
sommar@enea.UUCP "Si tu crois l'amour tabou...
Regarde bien, les yeux d'un fou!!!" -- Ange
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Path: arc1-ca.pugleaf.net!utzoo!mnetor!uunet!mcvax!enea!sommar From: sommar@enea.se (Erland Sommarskog) Newsgroups: comp.lang.misc Subject: Re: Var scoping in Wirth-type languages Message-ID: <2832@enea.se> Date: 11 Mar 88 21:22:24 GMT References: <2791@enea.se> <3949@ihlpf.ATT.COM> Reply-To: sommar@enea.UUCP(Erland Sommarskog) Followup-To: comp.lang.misc Organization: ENEA DATA AB, Sweden Lines: 33