In this case, I could have used pair's operator<, but if I have a class by value as the second item of the pair that doesn't have a meaningful operator<, I want to ignore it in the sort. Thanks for all the help, guys. Chris -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Victor A. Wagner Jr. Sent: Friday, March 26, 2004 8:40 AM To: boost-users@lists.boost.org Subject: Re: [Boost-users] Defining less on member variables/functions 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" _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users