C++ STL set functions… and liquids that can write code

Are you badass with C++ STL? Then fix this…

#include <iostream>
#include <map>
#include <set>
#include <algorithm>
#include <ostream>
#include <iterator>

using namespace std;

int main()
{
  map<const char, int> A;
  A['a'] = 0;
  A['b'] = 5;
  A['c'] = 10;

  map<const char, int> B;
  B['b'] = 105;
  B['c'] = 110;
  B['d'] = 115;

  map<const char, int> C;

  set_difference(A.begin(), A.end(), B.begin(), B.end(), less<char>, inserter(C, C.begin()) );
  /*cout << "Set C (difference of A and B): ";
  copy(C.begin(), C.end(), ostream_iterator<const char*>(cout, " "));
  cout << endl;*/
}

<aeacides> lol
<aeacides> fulld: you reversed the order of the comparison functor with the insert iterator
<aeacides> set_difference(A.begin(), A.end(), B.begin(), B.end(), inserter(C, C.begin()), ltpairchar());
<fulld> aeacides: so basically… what you’re saying is I need more coffee :-)
<fulld> thanks
<aeacides> fulld: programmers are essentially machines which transform coffee into code
<fulld> I’m gonna blog that

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Comments

The official X thread

@fulldecent

You were very close to getting the solution.
From the version where you have the ltpairchar struct, change this line:
set_difference(A.begin(), A.end(), B.begin(), B.end(), ltpairchar, inserter(C, C.begin()) );
to:
set_difference(A.begin(), A.end(), B.begin(), B.end(), inserter(C, C.begin()), ltpairchar());
You needed the () operator after your struct, and you had the last two arguments out of order.

Tyler

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