Path: utzoo!attcan!uunet!mcvax!enea!kth!draken!Urd!newsuser
From: newsuser@LTH.Se (LTH network news server)
Newsgroups: comp.lang.c++
Subject: Re: C++ : A free lunch ?
Message-ID: <1988Oct31.120012.162@LTH.Se>
Date: 31 Oct 88 11:00:12 GMT
References: <4165@tekgvs.GVS.TEK.COM> <4762@polya.Stanford.EDU>
Reply-To: dag@Control.LTH.Se (Dag Bruck)
Organization: Dept. of Automatic Control, Lund Inst. of Technology, Sweden
Lines: 33

In article <4762@polya.Stanford.EDU> shap@polya.Stanford.EDU (Jonathan S. Shapiro) writes:
>I am a more than competent LISP and SmallTalk hacker 

Furthermore, Jonathan Shapiro is probably a more than competent C++ hacker.
Unless you know perfectly what you are doing, you may for example initialize
variables twice.  The ``error'' I typically do is as follows:

In a class constructor I initialize members by assigning values to them.
The problem is that some members are class objects with constructors; these
objects are first automatically initialized with default values, which are
then thrown away because I make the assignments.

>C++ is just as fast as C.  Anything you want to do in C++ generates
>code that is no more complicated than the equivalent C code would need
>to be to do the same job.  

My C++ generates a fair number of temporary variables in the C code it
produces.  I understand that these temps are required to guarantee the
semantics of C++, but unfortunately, my C compiler on the Sun can't
eliminate the redundant assignments.  I also suffer some space overhead.
Looking at the generated assembler code, I believe it would be safe to
remove some instructions, but I don't bother.

My general, unscientific, impression is that you may loose about 5% in
execution speed when you make a quick port from C to C++.

Dag Bruck

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