This is again a newbie question.   

I want to create a graph based on some input file.  I parse this file and in the code I want to check whether the link already exists

int current=strToInt(tokens[0]);
int numedges=strToInt(tokens[1]);
for(int i=0;i<numedges;i++){
Vertex first=vertex(current,*g);
int other=strToInt(tokens[3+i]);
Vertex second=vertex(other,*g);
pair<Edge, bool> result=boost::edge(first,second,*g);
if(!result.second){
boost::add_edge(first,second,*g);
}
}


tokens[0] is the id of the node, tokens[1] contains the number of edges this node is pointing to.  From tokens[3] until the end, one gets the nodes to which the current node is connected (stored in other)
As you can see I call the function boost::edge() to check whether there is already a link between first and second.  As soon as I do this I get an error in Xcode.

Does anyone know what I'm doing wrong here.  It probably something very simple but I don't see it.


Thanks in advance

Tom