C++

Forum

 
Sorting vectors with a compare function.

anotherghost (17)
I can't figure out why the following isn't working:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
 
#include <iostream>
#include <algorithm>
#include <vector>

struct turtle {
	turtle(){}
	turtle(Int_t f_i, Double_t t_i) : f(f_i), t(t_i) {}
	Int_t f;
	Double_t t;
	void Show() { cout << f << " " << t << "\n"; }
};

bool compare_turtle_t(turtle& a, turtle& b) {
	return (a.t < b.t);
}

void test() {
	vector<turtle> turtles;
	vector<turtle>::iterator i;
	
	turtle a(1,10);
	turtle b(2,13);
	turtle c(3,8);
	turtle d(4,24);
	turtle e(5,6);
	turtle f(6,17);
	
	turtles.push_back(a);
	turtles.push_back(b);
	turtles.push_back(c);
	turtles.push_back(d);
	turtles.push_back(e);
	turtles.push_back(f);
	
	for (i = turtles.begin(); i != turtles.end(); ++i) i->Show();
	
	cout << "\n";
	
	sort(turtles.begin(), turtles.end(), compare_turtle_t); // What is wrong with this part?

	for (i = turtles.begin(); i != turtles.end(); ++i) i->Show();
	
}


The output is


1 10
2 13
3 8
4 24
5 6
6 17

Internal error: template function call __median failed algo.h(748)
*** Interpreter error recovered ***


I've tried to use this virtually word for word from the sort reference page example : http://www.cplusplus.com/reference/algorithm/sort/

and have tried to use the advice given on this other forum post: http://www.cplusplus.com/forum/beginner/4817/

Also, I should note it gives me the same error whether compare_turtle_t takes hit or hit&.

But I still can't figure out what I'm doing wrong. I feel like I've got to be pretty close but I'm not sure what's going on.
Last edited on
Galik (2254)
Try:
1
2
3
 
bool compare_turtle_t(const turtle& a, const turtle& b) {
	return (a.t < b.t);
}
anotherghost (17)
Same error.
Galik (2254)
That's odd, it works fine for me. Can you post the whole error message?
anotherghost (17)
That is the whole error message. Lol.

The compiler I'm using is ROOT - could that have something to do with it?
Galik (2254)
I've never used ROOT. Perhaps you could try:
 
 
	sort(turtles.begin(), turtles.end(), &compare_turtle_t);

Otherwise I'm stumped.
anotherghost (17)
That didn't work either. I changed it around a little bit and got a different error... took out the compare_turtle_t function and instead defined a < for turtles:

1
2
3
4
5
6
7
8
9
10
11
 
struct turtle {
	...
	bool operator<(turtle rhs) { return (t < rhs.t); }
	...
};

void test() {
	...
	sort(turtles.begin(), turtles.end());
	...
}


Now I'm getting

1 10
2 13
3 8
4 24
5 6
6 17

Error: Function __linear_insert(first,i,value_type(first)) is not defined in cur
rent scope  algo.h(814)
*** Interpreter error recovered ***


Does that help at all?
Last edited on
closed account (DSLq5Di1)
http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=6336
http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=12932

Seems to be an issue with the interpreter.
Topic archived. No new replies allowed.