Re: problem with sort

From:
Kai-Uwe Bux <jkherciueh@gmx.net>
Newsgroups:
comp.lang.c++
Date:
Wed, 14 Jun 2006 15:00:50 +0200
Message-ID:
<e6p1ap$335$1@murdoch.acc.Virginia.EDU>
Gaijinco wrote:

I'm not quite sure why this code doesn't works:

#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
using namespace std;

class word
{
 string letters;
 string sorted;
 public:
 word(string&s)
 {
    letters=s;
    sort(s.begin(),s.end());
    sorted=s;
 }


Are you sure, you want this constructor to have the side-effect of sorting
the parameter passed? What about:

 word ( string const & s )
   : letters ( s )
   , sorted ( s )
 {
    sort( sorted.begin(), sorted.end() );
 }

 friend bool lt(word& a, word& b)
 {
   return (a.sorted < b.sorted) < 0 ? true: false;


Huh? operator< returns a bool, it is not a three-way comparison yielding an
int. What about:

    return ( a.sorted < b.sorted );

 }
 friend ostream& operator<<(ostream& out, vector<word>& v)


This should be:

friend ostream& operator<< ( ostream& out, vector<word> const & v )

unless you want the output operator to modify its argument.

 {
   for(int i=0; i<v.size(); ++i)
      cout << v[i].letters << endl;
   return out;
 }
};

int main()
{
  vector<word>dict;
  string aux;
  cin >> aux;

  while(aux!="#")
  {
     word w(aux);
     dict.push_back(w);

     cin >> aux;
  }

  sort(dict.begin(),dict.end(),lt);
  cout << dict << endl;

    return 0;
}

There's something wrong with the function "lt" but i'm not sure what.
In the prototype it says:
StrictWeakOrdering cmp but I'm not sure what does that mean, maybe
something about the kind of iterators I need to use?


Soring a dictionary according to the lexicographic order of internally
rearranged words seems to be a rather strange requirement. Are you sure,
your want that?

Best

Kai-Uwe Bux

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