Re: [boost] Interest in super string class?

From: Marc Mutz (marc_at_[hidden])
Date: 2006-07-02 15:36:02

On Sunday 02 July 2006 03:03, Jeff Garland wrote:
>    super_string s("    (456789) [123]  2006-10-01    abcdef   ");
>    s.to_upper();
>    cout << s << endl;
>
>    s.trim();  //lop of the whitespace on both sides
>    cout << s << endl;

I really like this proposal, but have a minor point to add:
IMHO, value classes should have much fewer mutating (non-const) (member) 
functions. The above two examples are a very good example. to_upper() should 
be const and return the string converted to uppercase, instead of performing 
the operation on 'this'. Similarly, trim() should be trim_med_() and return a 
trimmed copy of 'this'. This makes it much easier to work with such classes. 
Qt4's QString has gone a long way towards this style of interface, but still 
has a lot of annoying exceptions that make me mad most every day.

The usual argument against is performance, and I agree performance is 
important for a general-purpose string class. But what is often overlooked is 
that the prefer-const-to-mutable-methods-style interface allows many more 
optimisations than the classical style, if the implementor is willing to go 
down the expression template path:
  s = s.replace('&',"&amp;").replace('<',"&lt;).replace('\'','&apos;');
can be made to execute a lot faster if replace is const than if it is not, b/c 
it forces the return value of replace() to be evaluated.

Maybe I'm talking common wisdom here, it's just something that I found 
annoying in my everyday work and wanted to share. Feel free to ignore :)

Thanks,
Marc

-- 
Marc Mutz -- marc_at_[hidden], mutz_at_[hidden]
Klarälvdalens Datakonsult AB, Platform-independent software solutions