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>)'

For more info, see [this question](http://stackoverflow.com/q/19375634/1782465). — Angew is no longer proud of SO, Oct 17 '13 at 10:10

score 3 · Accepted Answer · answered Oct 17 '13 at 09:55

3

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.

answered Oct 17 '13 at 09:55

Luchian Grigore

253,575
64
457
625

Small correction: "a temporary can't bind to a non-const **lvalue** reference." (Recall that a temporary can bind to a non-const **rvalue** reference.) – Cassio Neri Oct 17 '13 at 10:08

Inconsistent behaviour passing arguments in C++

1 Answers1