Re: [Boost-users] Using Boost string library

From: Meryl Silverburgh (silverburgh.meryl_at_[hidden])
Date: 2007-02-17 20:52:24

Thanks for your idea.

I have cases like this:

/1/1
/1/2/3/2

Since the first string /1/1 is smaller than the /1/2 (1 is < 2) of the
/1/2/3/2, I should able to stop comparison by looking at the 4th
character (/1/2) of '/1/2/3/2'.

So for cases like that, I would like to stop as soon as i can tell one
string is shorter than the other, instead of splitting the whole
string.

On 2/17/07, Pavol Droba <droba_at_[hidden]> wrote:
> Hi,
>
> Meryl Silverburgh wrote:
> > Hi,
> >
> > I need to compare 2 strings in this format (a integer separator by '/':
> > /1/1
> > /1/1/2
> > /1/1/3
> >
> > so
> > "/1/1" is less than "/1/1/2" and  "/1/1/2" is less than " "/1/1/3".
> >
> > Is there anything in Boost string library to help me to write such a comparison?
> > Is there a string iterator which literates base on the separator '/'?
> > My idea is to find an iterator to loop thru the string based on
> > separator '/'.
>
> There is a split_iterator which you can use. And there is a generic
> lexicographical_compare function.
>
> I've got an idea that might work. But it is a little elaborate.
> First, tokenize your string using split, but store the result to
> vector<iterator_range>.
>
> Then define a comparison function, that will take the two
> iterator_ranges and compare them. Note, that in this case, tha range
> should hold an integer string.
> Then simply use lexicographical_compare for the comparison.
>
>
> vector<iterator_range> vec1;
> split(vec, s1);
> vector<iterator_range> vec2;
> split(vec, s2);
> if(lexicographical_compare(vec1, vec2, integer_compare))
> {
>         // s1 is less
> }
>
> You can even throw away the vector, and directly create an
> iterator_range from the split_iterator. This way you may spare some
> unnecessary tokenization.
>
> typedef split_iterator<string::const_iterator> string_split;
> iterator_range<string_split> r1(
>         make_split_iterator(s1, is_any_of("/")), string_split())
>
> iterator_range<string_split> r2(
>         make_split_iterator(s2, is_any_of("/")), string_split())
>
> if(lexicographical_compare(vec1, vec2, integer_compare))
> {
>         // s1 is less
> }
>
> Best Regards,
> Pavol.
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