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From: Jeff Garland (jeff_at_[hidden])
Date: 2006-07-02 17:09:12

Marc Mutz wrote:
> 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.

Well, I went about 50% of the way on this. You'll notice that for some things
there are non-modifying variations.

   basic_super_string trim_copy() const;
   basic_super_string trim_left_copy() const;
   basic_super_string trim_right_copy() const;

   basic_super_string to_lower_copy() const;
   basic_super_string to_upper_copy() const;

I just got tired and didn't add all the variations for replace_xxx. Of course
that makes the interface even fatter :-)

> 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.

I'm no expert in expression templates, but I don't think '.' can be overloaded
-- how can ET do anything here?

> 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 :)

I'll add replace_*_copy versions in the next rev...


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