Re: [Boost-users] Defining less on member variables/functions

From: Victor A. Wagner Jr. (vawjr_at_[hidden])
Date: 2004-03-26 11:40:17

why do you want to sort ONLY on the 1st element of the pair?

At Thursday 2004-03-25 11:34, you wrote:
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>I've had this same pattern come up 4 or 5 times now, and each time I've 
>been unable to find a stl + boost solution that allowed me to do what I 
>want without writing my own less function.  Basically, I want something 
>that will let me do a sort, or define a map on structs or pairs without 
>writing a less that compares the member variable or ..first.  My last attempt:
>
>vector<pair<float, float>> myVector
>std::sort(myVector.begin(), myVector.end(), _1.first < _2.first);
>
>No such luck.  It looks like I can do operator * and & on lambda objects, 
>but not access members through them.  Is there anything in boost, stl, or 
>elsewhere that lets me not write this:
>
>class myLess
>{
>     bool operator() (pair<float, float> a, pair<float, float>b)
>         {return a.first < b.first;}
>}
>
>Thanks for any help,
>Chris
>
>
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Victor A. Wagner Jr.      http://rudbek.com
The five most dangerous words in the English language:
               "There oughta be a law"