Expected primary-expression before ‘&’ token

up vote
-1
down vote

favorite

I receive this error that makes it difficult for me to continue coding, because I tried and tried to solve it and was unable to understand what the error means (I looked at similar questions in Stackoverflow).

I do not understand why, if I declare a set of Node objects as a type of data, I get these errors, code:

point p(p.get_x(),p.get_y());





Node a(p,0); 



set<Node&> visited_nodes;

The error:

error: expected primary-expression before ‘&’ token

         set<Node&> visited_nodes;

                 ^

error: expected primary-expression before ‘>’ token

         set<Node&> visited_nodes;

Thanks

edited Nov 11 at 22:35

Matthieu Brucher

9,80421834

asked Nov 11 at 22:12

AER

1117

Please provide a Minimal, Complete, and Verifiable example. The best anyone can do right now is guess.
– chris
Nov 11 at 22:14

2

I would guess you either need to #include <set> or using std::set.
– aschepler
Nov 11 at 22:39

@aschleper, set library already included before i post the question. Thanks
– AER
Nov 11 at 22:42

add a comment |

up vote
-1
down vote

favorite

I do not understand why, if I declare a set of Node objects as a type of data, I get these errors, code:

point p(p.get_x(),p.get_y());





Node a(p,0); 



set<Node&> visited_nodes;

The error:

error: expected primary-expression before ‘&’ token

         set<Node&> visited_nodes;

                 ^

error: expected primary-expression before ‘>’ token

         set<Node&> visited_nodes;

Thanks

edited Nov 11 at 22:35

Matthieu Brucher

9,80421834

asked Nov 11 at 22:12

AER

1117

Please provide a Minimal, Complete, and Verifiable example. The best anyone can do right now is guess.
– chris
Nov 11 at 22:14

2

I would guess you either need to #include <set> or using std::set.
– aschepler
Nov 11 at 22:39

@aschleper, set library already included before i post the question. Thanks
– AER
Nov 11 at 22:42

add a comment |

up vote
-1
down vote

favorite

I do not understand why, if I declare a set of Node objects as a type of data, I get these errors, code:

point p(p.get_x(),p.get_y());





Node a(p,0); 



set<Node&> visited_nodes;

The error:

error: expected primary-expression before ‘&’ token

         set<Node&> visited_nodes;

                 ^

error: expected primary-expression before ‘>’ token

         set<Node&> visited_nodes;

Thanks

edited Nov 11 at 22:35

Matthieu Brucher

9,80421834

asked Nov 11 at 22:12

AER

1117

I do not understand why, if I declare a set of Node objects as a type of data, I get these errors, code:

point p(p.get_x(),p.get_y());





Node a(p,0); 



set<Node&> visited_nodes;

The error:

error: expected primary-expression before ‘&’ token

         set<Node&> visited_nodes;

                 ^

error: expected primary-expression before ‘>’ token

         set<Node&> visited_nodes;

Thanks

c++ oop object compilation set

edited Nov 11 at 22:35

Matthieu Brucher

9,80421834

asked Nov 11 at 22:12

AER

1117

edited Nov 11 at 22:35

Matthieu Brucher

9,80421834

asked Nov 11 at 22:12

AER

1117

edited Nov 11 at 22:35

Matthieu Brucher

9,80421834

edited Nov 11 at 22:35

Matthieu Brucher

9,80421834

edited Nov 11 at 22:35

Matthieu Brucher

9,80421834

asked Nov 11 at 22:12

AER

1117

asked Nov 11 at 22:12

AER

1117

asked Nov 11 at 22:12

AER

1117

Please provide a Minimal, Complete, and Verifiable example. The best anyone can do right now is guess.
– chris
Nov 11 at 22:14

2

I would guess you either need to #include <set> or using std::set.
– aschepler
Nov 11 at 22:39

@aschleper, set library already included before i post the question. Thanks
– AER
Nov 11 at 22:42

add a comment |

Please provide a Minimal, Complete, and Verifiable example. The best anyone can do right now is guess.
– chris
Nov 11 at 22:14

2

I would guess you either need to #include <set> or using std::set.
– aschepler
Nov 11 at 22:39

@aschleper, set library already included before i post the question. Thanks
– AER
Nov 11 at 22:42

Please provide a Minimal, Complete, and Verifiable example. The best anyone can do right now is guess.
– chris
Nov 11 at 22:14

I would guess you either need to #include <set> or using std::set.
– aschepler
Nov 11 at 22:39

@aschleper, set library already included before i post the question. Thanks
– AER
Nov 11 at 22:42

add a comment |

1 Answer
1

active

oldest

votes

up vote
1
down vote

accepted

You cannot store references at containers. You should store pointers or the objects.

EDIT:
After chat session, we discovered the cause.
He was having a name conflict due to using namespace std;.

So I proposed:

std::set<Node> visited_nodes;

And the error dissapeared.

edited Nov 11 at 23:08

answered Nov 11 at 22:14

LuisGP

336110

2

While true, the question is about a syntax error.
– chris
Nov 11 at 22:15

2

The error is related. As std::set is a templated class, I think the most clearer way to resolve his problem is to advice him that he cannot store references. More details can be confusing.
– LuisGP
Nov 11 at 22:34

3

I don't see how the error is related at all. It's perfectly legal syntax to pass a reference as a template argument and the compiler is getting hung up on parsing. The only reason this is a problem is due to specific requirements on std::set (and other standard containers) about which types they support.
– chris
Nov 11 at 22:38

@LuisGP When i change it to that : set<Node> visited_nodes; , i get this error: expected primary-expression before ‘>’ token
– AER
Nov 11 at 22:38

@AER then probably @aschepler is right. Did you included set or using std::set?
– LuisGP
Nov 11 at 22:40

|
show 5 more comments

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
1
down vote

accepted

You cannot store references at containers. You should store pointers or the objects.

EDIT:
After chat session, we discovered the cause.
He was having a name conflict due to using namespace std;.

So I proposed:

std::set<Node> visited_nodes;

And the error dissapeared.

edited Nov 11 at 23:08

answered Nov 11 at 22:14

LuisGP

336110

2

While true, the question is about a syntax error.
– chris
Nov 11 at 22:15

2

The error is related. As std::set is a templated class, I think the most clearer way to resolve his problem is to advice him that he cannot store references. More details can be confusing.
– LuisGP
Nov 11 at 22:34

3

I don't see how the error is related at all. It's perfectly legal syntax to pass a reference as a template argument and the compiler is getting hung up on parsing. The only reason this is a problem is due to specific requirements on std::set (and other standard containers) about which types they support.
– chris
Nov 11 at 22:38

@LuisGP When i change it to that : set<Node> visited_nodes; , i get this error: expected primary-expression before ‘>’ token
– AER
Nov 11 at 22:38

@AER then probably @aschepler is right. Did you included set or using std::set?
– LuisGP
Nov 11 at 22:40

|
show 5 more comments

up vote
1
down vote

accepted

You cannot store references at containers. You should store pointers or the objects.

EDIT:
After chat session, we discovered the cause.
He was having a name conflict due to using namespace std;.

So I proposed:

std::set<Node> visited_nodes;

And the error dissapeared.

edited Nov 11 at 23:08

answered Nov 11 at 22:14

LuisGP

336110

2

While true, the question is about a syntax error.
– chris
Nov 11 at 22:15

2

The error is related. As std::set is a templated class, I think the most clearer way to resolve his problem is to advice him that he cannot store references. More details can be confusing.
– LuisGP
Nov 11 at 22:34

3

I don't see how the error is related at all. It's perfectly legal syntax to pass a reference as a template argument and the compiler is getting hung up on parsing. The only reason this is a problem is due to specific requirements on std::set (and other standard containers) about which types they support.
– chris
Nov 11 at 22:38

@LuisGP When i change it to that : set<Node> visited_nodes; , i get this error: expected primary-expression before ‘>’ token
– AER
Nov 11 at 22:38

@AER then probably @aschepler is right. Did you included set or using std::set?
– LuisGP
Nov 11 at 22:40

|
show 5 more comments

up vote
1
down vote

accepted

You cannot store references at containers. You should store pointers or the objects.

EDIT:
After chat session, we discovered the cause.
He was having a name conflict due to using namespace std;.

So I proposed:

std::set<Node> visited_nodes;

And the error dissapeared.

edited Nov 11 at 23:08

answered Nov 11 at 22:14

LuisGP

336110

You cannot store references at containers. You should store pointers or the objects.

EDIT:
After chat session, we discovered the cause.
He was having a name conflict due to using namespace std;.

So I proposed:

std::set<Node> visited_nodes;

And the error dissapeared.

edited Nov 11 at 23:08

answered Nov 11 at 22:14

LuisGP

336110

edited Nov 11 at 23:08

answered Nov 11 at 22:14

LuisGP

336110

answered Nov 11 at 22:14

LuisGP

336110

answered Nov 11 at 22:14

LuisGP

336110

2

While true, the question is about a syntax error.
– chris
Nov 11 at 22:15

2

The error is related. As std::set is a templated class, I think the most clearer way to resolve his problem is to advice him that he cannot store references. More details can be confusing.
– LuisGP
Nov 11 at 22:34

3

I don't see how the error is related at all. It's perfectly legal syntax to pass a reference as a template argument and the compiler is getting hung up on parsing. The only reason this is a problem is due to specific requirements on std::set (and other standard containers) about which types they support.
– chris
Nov 11 at 22:38

@LuisGP When i change it to that : set<Node> visited_nodes; , i get this error: expected primary-expression before ‘>’ token
– AER
Nov 11 at 22:38

@AER then probably @aschepler is right. Did you included set or using std::set?
– LuisGP
Nov 11 at 22:40

|
show 5 more comments

2

While true, the question is about a syntax error.
– chris
Nov 11 at 22:15

2

The error is related. As std::set is a templated class, I think the most clearer way to resolve his problem is to advice him that he cannot store references. More details can be confusing.
– LuisGP
Nov 11 at 22:34

3

I don't see how the error is related at all. It's perfectly legal syntax to pass a reference as a template argument and the compiler is getting hung up on parsing. The only reason this is a problem is due to specific requirements on std::set (and other standard containers) about which types they support.
– chris
Nov 11 at 22:38

@LuisGP When i change it to that : set<Node> visited_nodes; , i get this error: expected primary-expression before ‘>’ token
– AER
Nov 11 at 22:38

@AER then probably @aschepler is right. Did you included set or using std::set?
– LuisGP
Nov 11 at 22:40

While true, the question is about a syntax error.
– chris
Nov 11 at 22:15

The error is related. As std::set is a templated class, I think the most clearer way to resolve his problem is to advice him that he cannot store references. More details can be confusing.
– LuisGP
Nov 11 at 22:34

I don't see how the error is related at all. It's perfectly legal syntax to pass a reference as a template argument and the compiler is getting hung up on parsing. The only reason this is a problem is due to specific requirements on std::set (and other standard containers) about which types they support.
– chris
Nov 11 at 22:38

@LuisGP When i change it to that : set<Node> visited_nodes; , i get this error: expected primary-expression before ‘>’ token
– AER
Nov 11 at 22:38

@AER then probably @aschepler is right. Did you included set or using std::set?
– LuisGP
Nov 11 at 22:40

|
show 5 more comments

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