Survey Results

list::sort
void sort();
template<class Pred>
    void sort(greater<T> pr);

Chris Losinger wrote:
I can't use std::list to sort a list by arbitrary predicates

???

of course you can.
list::sortvoid sort();template void sort(greater pr);


just because the parameter is called "greater" on the function prototype doesn't mean it can't be comparing in whatever direction you want. if fact, the sample for list::sort shows how to sort with a custom predicate.

#include <iostream>
#include <list>
 
using namespace std;
 
struct Foo
{
 int m_nValue;
 Foo(int val = 0) : m_nValue(val) {}
 bool operator >(const Foo& rhs_) const;
 bool operator <(const Foo& rht_) const;
 bool greater_mag(const Foo& rht_) const;
};
 
bool Foo::operator <(const Foo& rhs_) const
{
 return m_nValue < rhs_.m_nValue;
}
 
bool Foo::operator >(const Foo& rhs_) const
{
 cerr << "Called >" << endl;
 return (m_nValue > rhs_.m_nValue);
}
 
bool Foo::greater_mag(const Foo& rhs_) const
{
 cerr << "Called greater_mag" << endl;
 return abs(m_nValue) > abs(rhs_.m_nValue);
}
 
template <class T_> struct greater_magnitude : public greater<T_>
{
 bool operator()(const T_& x, const T_& y) const {
  return (x.greater_mag(y));
  }
};
 
int main(int argc, char* argv[])
{
 list<Foo> flist;
 flist.push_back(Foo(1));
 flist.push_back(Foo(-2));
 flist.push_back(Foo(3));
 
 flist.sort(greater_magnitude<Foo>());
 list<Foo>::const_iterator it = flist.begin();
 while (it != flist.end())
  cout << it++ ->m_nValue << " ";
 cout << endl;
 return 0;
}

Called >
Called >
3 1 -2

Called greater_mag
Called greater_mag
3 -2 1

Main Entry:	blue streak
Function:	noun
Date:	1830
1 : something that moves very fast
2 : a constant stream of words  (talked a blue streak)

Main Entry:	blue 
Pronunciation:	'blü
Function:	adjective
Inflected Form(s):	blu·er; blu·est

Etymology:	Middle English, from Old French blou, of Germanic origin; akin to Old High German blAo blue; akin to Latin flavus yellow
Date:	13th century

1 : of the color blue
2 a : BLUISH b : discolored by or as if by bruising  (blue with cold) c : bluish gray  (blue cat)

3 a : low in spirits : MELANCHOLY b : marked by low spirits : DEPRESSING (blue funk)  (things looked blue)

4 : wearing blue
5 of a woman : LEARNED, INTELLECTUAL
6 : PURITANICAL

7 a : PROFANE, INDECENT (blue movie) b : OFF-COLOR, RISQUé (blue jokes)

8 : of, relating to, or used in blues  (blue song)