Re: [boost] Re: [Libcwd-devel] libcwd and Boost

From: Thomas Witt (witt_at_[hidden])
Date: 2002-08-30 10:46:26

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On Friday 30 August 2002 16:52, Carlo Wood wrote:
> On Fri, Aug 30, 2002 at 03:54:20PM +0200, Thomas Witt wrote:
> > > void demangle_type(std::string & t_o, std::string const & t_i);
> > > void demangle_symbol(std::string & s_o, std::string const & s_i);
> >
> > Take my apologies for the possibly dumb question, but what's wrong with
> >
> > std::string demangle_type(std::string const & t_i);
>
> The function appends its data to the string.

- From a usability point of view this kind of interface is very problematic (to 
say the least). Not only has the user (and the maintenance programmer) to 
remember where the "hidden" output parameter is (btw it's completely 
invisible at the call site). He has to remember the "non-obvious" semantics 
as well. Unless there is a compelling reason I would not like to see this 
kind of interface in the public part of a library.

> This allows to 'construct' a string without unnecessary
> need to copy strings.
>
> For example:
>
> std::string out = "You are inside ";
> demangle(out, mangled_function_name);

The blunt answer would be : "Hooray you have managed to save a string copy in 
debug code, so what?". Seriously I don't think it's worth it. Furthermore I 
think that there is a good chance of your claim being wrong.

Somewhere inside demangle you might write something like this:

t_o += demangled_name;

Depending on the history of t_o this might trigger an allocation and a string 
copy.

>
> Your prototype can always be added as a wrapper without extra cost.

This is interface bloat. The ideal library API presents exactly one way to 
perform a certain task.

Regards

- --Thomas

- -- 
Dipl.-Ing. Thomas Witt
Institut fuer Verkehrswesen, Eisenbahnbau und -betrieb, Universitaet Hannover
voice: [phone] - 4273, fax: [phone]
http://www.ive.uni-hannover.de
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