Inconsistent behaviour passing arguments in C++

Question

Given these two function declarations:

void initialize(int p, std::vector<Vector3> &);
std::vector<Vector3> toNurbsCoords(std::vector<Vector3>);

why does this work

Nurbs nurbs;
std::vector<Vector3> pts = nurbs.toNurbsCoords(points);
nurbs.initialize(degree, pts);

while this throws a compile time error?

Nurbs nurbs;    
nurbs.initialize(degree, nurbs.toNurbsCoords(points));
//error: no matching function for call to 'Nurbs::initialize(int&, std::vector<Vector3>)'

Answer 1

Because a temporary can't bind to a non- const reference.

nurbs.toNurbsCoords(points) is a temporary. In the first case you initialize named object - pts - with it and pass that. In the second case, you just pass the temp.