Re: [Boost-users] Using Boost string library

From: Pavol Droba (droba_at_[hidden])
Date: 2007-02-17 17:17:42

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.