C++ help with STL - sort() function

Question

Another small question about STL:

i have Dictionary:

map <string,vector <Wordy> > Dictionary;

using structure Wordy:

struct Wordy{ int count; string word;}

also this structure have overloaded operator<

bool operator< (Wordy& One, Wordy& Two){return One.count<Two.count;}

but this sort() function from algorithm doesn't work!

sort(Dictionary.find(s)->second.begin(),Dictionary.find(s)->second.end());

@Martin: The OP isn't sorting the map, she's sorting a particular *element* of the map. — Kerrek SB, Jul 04 '11 at 23:43

score 8 · Accepted Answer · answered Jul 04 '11 at 21:00

8

Your operator< should take its parameters by reference-to-const, I think that might be it:

bool operator< (const Wordy& One, const Wordy& Two){return One.count<Two.count;}
//              ^^^^^             ^^^^^

answered Jul 04 '11 at 21:00

Xeo

score 0 · Answer 2 · edited May 23 '17 at 12:04

0

check the post How to use std::sort with a vector of structures and compare function? . it explains how to use sort with a customized predicate function

edited May 23 '17 at 12:04

Community

answered Jul 04 '11 at 20:58

NirMH

1

I don't think that's it. That question deals with a sort function that wasn't returning bool. – zdan Jul 04 '11 at 21:00
Why should you need a custom predicate, if you can (and want) to implement `operator<`? – Kerrek SB Jul 04 '11 at 21:01
@zdan: do you mean the `bool operator<(...)` function? – NirMH Jul 04 '11 at 21:02
@NirMH: Yes, I meant the sort "predicate" not the sort function. – zdan Jul 04 '11 at 22:07

2 Answers2