Re: [boost] Does Boost has an utility to replace all OLD Keys with NEW one for MultiMap/Map?

Subject: Re: [boost] Does Boost has an utility to replace all OLD Keys with NEW one for MultiMap/Map?
From: Tushar Chowdhury (tchowdhury80_at_[hidden])
Date: 2009-05-08 10:28:18

wonderful. Thanks guys.

On Fri, May 8, 2009 at 10:27 AM, Tushar Chowdhury <tchowdhury80_at_[hidden]>wrote:

>
>
> On Thu, May 7, 2009 at 2:05 PM, Duncan Smith <duncanphilipnorman_at_[hidden]
> > wrote:
>
>> 2009/5/7 Phil Endecott <spam_from_boost_dev_at_[hidden]>
>> > template <typename CONT>
>> > void replace_key(CONT& cont, typename CONT::key_type oldk, typenamme
>> CONT::key_type newk)
>> > {
>> >  if (newk==oldk) return;
>> >
>> >  typedef typename CONT::iterator iter;
>> >  std::pair<iter,iter> r = cont::equal_range(oldk);
>> >  iter hint = cont.begin();
>> >  for (iter i = r.first; i != r.second; ++r) {
>> >    hint = cont.insert(hint,std::make_pair(newk,i->second));
>> >  }
>> >  cont.erase(r.first,r.second);
>> > }
>> As Phil mentioned, the range returned from 'equal_range()'  will
>> expand when you do 'cont.insert()' if the oldk < newk < (the next key
>> larger than oldk), causing an infinite loop during insertion.  Then,
>> both sets of keys will get erased with 'erase()'.
>>
>> The easiest way to do this robustly is with temporary storage:
>>
>> #include <algorithm>
>> #include <boost/bind.hpp>
>> #include <boost/ref.hpp>
>> #include <utility>
>> #include <vector>
>>
>> template <typename Container>
>> void replace_key(Container &c, typename Container::key_type oldKey,
>> typename Container::key_type newKey)
>> {
>>  if (oldKey != newKey) {
>>    typedef typename Container::iterator iterator;
>>    typedef typename Container::value_type value_type;
>>    typedef typename Container::key_type key_type;
>>    typedef typename Container::mapped_type mapped_type;
>>    using ::std::make_pair;
>>    using ::std::vector;
>>    using ::boost::bind;
>>    using ::boost::cref;
>>    using ::std::transform;
>>
>>    std::pair<iterator, iterator> range = c.equal_range(oldKey);
>>    std::vector<mapped_type> values;
>>    transform(range.first, range.second,
>>      std::back_inserter(values),
>>      bind(&value_type::second, _1));
>>
>>    c.erase(range.first, range.second);
>>
>>    transform(values.begin(), values.end(),
>>      std::inserter(c, c.end()),
>>      bind(make_pair<key_type, mapped_type>, cref(newKey), _1));
>>  }
>> }
>>
>> There are more efficient implementations, but this should do it.
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>
>