[C++] Help I'm retarded

I

Iamtehwalrus

Veteran XV
If you're bored, feel free to help me :D
i suck at coding, and i'm prolly gonna give it up (cuz y'know... i suck)

anyway, I'm trying to make a priority queue (with the min at the node) for this class I made, and I don't know how exactly to implement the comparing part. What I have already is probably retarded and hence doesn't compile

I've included the important parts--tell me if i should include more (and this is all in a header file if u couldn't tell). Pink code are the key parts
Code: 
#include <vector>
#include <list>
#include <queue>
#include <iterator>

template <typename T>
struct Edge
{
    Edge(T vertex1, T vertex2, double cost) {
        v1 = vertex1;
        v2 = vertex2;
        distance = cost;
    }
    T v1;
    T v2;
    double distance;
[color=pink]    bool operator> (const Edge<T>& param) {
        return (distance>param.distance);
    }[/color]
};

template <typename T>
class Graph
{
    public:
        //...
        int partition(int);
        //...
    private:
        std::vector<T> vertices;
        std::list< Edge<T> > edges;
};

//...

template <typename T>
int Graph<T>::partition(int clusterMax) {
[color=pink]    std::priority_queue< Edge<T> > pq(edges.begin(), edges.end(), std::greater< Edge<T> >);
//    std::priority_queue< Edge<T>, std::vector< Edge<T> >, std::greater< Edge<T> > > pq;[/color]
    return 0;
}

Errors if compiled as is:
Code: 
58 C:\CS311\PA4\graph.hpp expected primary-expression before ')' token
Line 58: is
Code: 
std::priority_queue< Edge<T> > pq(edges.begin(), edges.end(), std::greater< Edge<T> >);

errors if I use the commented PQ constructor instead:
Code: 
 C:\Dev-Cpp\include\c++\3.4.2\bits\stl_function.h In member function `bool std::greater<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = Edge<Sample>]': 
279 C:\Dev-Cpp\include\c++\3.4.2\bits\stl_heap.h   instantiated from `void std::__adjust_heap(_RandomAccessIterator, _Distance, _Distance, _Tp, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Edge<Sample>*, std::vector<Edge<Sample>, std::allocator<Edge<Sample> > > >, _Distance = int, _Tp = Edge<Sample>, _Compare = std::greater<Edge<Sample> >]' 
404 C:\Dev-Cpp\include\c++\3.4.2\bits\stl_heap.h   instantiated from `void std::make_heap(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Edge<Sample>*, std::vector<Edge<Sample>, std::allocator<Edge<Sample> > > >, _Compare = std::greater<Edge<Sample> >]' 
369 C:\Dev-Cpp\include\c++\3.4.2\bits\stl_queue.h   instantiated from `std::priority_queue<_Tp, _Sequence, _Compare>::priority_queue(const _Compare&, const _Sequence&) [with _Tp = Edge<Sample>, _Sequence = std::vector<Edge<Sample>, std::allocator<Edge<Sample> > >, _Compare = std::greater<Edge<Sample> >]' 
59 C:\CS311\PA4\graph.hpp   instantiated from `int Graph<T>::partition(int) [with T = Sample]' 
90 C:\CS311\PA4\test_mst.cpp   instantiated from here 
218 C:\Dev-Cpp\include\c++\3.4.2\bits\stl_function.h passing `const Edge<Sample>' as `this' argument of `bool Edge<T>::operator>(const Edge<T>&) [with T = Sample]' discards qualifiers 
 C:\CS311\PA4\Makefile.win [Build Error]  [test_mst.o] Error 1
line 59 is:
Code: 
std::priority_queue< Edge<T>, std::vector< Edge<T> >, std::greater< Edge<T> > > pq;

I'm not sure exactly how to make a PQ, so I just tried all the things I saw on google. Ideally what I want is a min-heap priority queue (with min at the root) with a list of Edge<T>'s that I have (edges is the variable).

Any ideas?

:sunny:
 
Last edited:
go to line 58 and check to see that you formatted what ever expression is there properly. Since you cut and paste i'm pretty sure the line 58 i count to would not be line 58 of your code.

EDIT: nm that 58 doesn't appear to be a line indicator... get a better compiler that doesn't leave criptic messages for starters. But as far as i can tell you have formatted an argument improperly.
 
telos said:
go to line 58 and check to see that you formatted what ever expression is there properly. Since you cut and paste i'm pretty sure the line 58 i count to would not be line 58 of your code.
Click to expand...

yeah sorry that was retarded
line 58:
Code: 
std::priority_queue< Edge<T> > pq(edges.begin(), edges.end(), std::greater< Edge<T> >);
 
what is the pq() asking for as arguments? it looks like you are sending it (int, int, what ever greater<> returns) try determining the greater number outside the pq argument and stick the result in there.

I'm not all that good at this but thats where i would start
 
telos said:
what is the pq() asking for as arguments? it looks like you are sending it (int, int, what ever greater<> returns) try determining the greater number outside the pq argument and stick the result in there.

I'm not all that good at this but thats where i would start
Click to expand...

i might be wrong but I thought i was creating a priority queue named pq... so pq isn't a function
I was basing it off this constructor
Code: 
priority_queue ( InputIterator first, InputIterator last, const Compare& x = Compare(), const Container& y = Container() );
from priority_queue::priority_queue - C++ Reference

I guess I don't really know what the priority_queue constructor is. A lot of things are different on google, and it confuses me. It seems the commented pq constructor i have might be the "proper" way but i don't really know
 
Bohica said:
Standard Template Library Programmer's Guide

priority_queue<T, Sequence, Compare>
Click to expand...

priority_queue(const value_type* first, const value_type* last, const Compare& comp)
Click to expand...
yeah this is what I was trying to use. i'm really bad at syntax and i forget basic things, so it wouldn't surprise me if i'm not using it correctly

EDIT:
I guess I don't know waht to put the for comparison argument. For some reason I got the idea I could just put greater<> or less<> and it would work fine as long as I overloaded the opeartor> for my class
 
Last edited:
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