C++ Using default values for parameters

Question

I am new to C++ (from C# background) and I have a function with the following signature

 void AddBenchNode(ref_ptr<Group> root ,ref_ptr<Node> benches, bool setAttitude = false, float scale_x =.15, float scale_y =15, float scale_z = 15, int positionx = 250, int positiony = 100, int positionz =0 )
{

}

But when I try to call the code as below, I get an error which says function does not take 4 arguments.

//then I try to call my function like so
AddBenchNode(root, benches, false, 250);

but I instead get the following error message

error C2660: 'AddBenchNode' : function does not take 3 arguments

Would appreciate an explanation of how C++ does this instead?

The default parameters should be declared in the header file, not in the implementation file. — n. m. could be an AI
– n. m. could be an AI, Commented Jul 5, 2012 at 14:15
You should provide a minimal self-contained compiling example everyone can take and try for themselves to see what you see. — PlasmaHH
– PlasmaHH, Commented Jul 5, 2012 at 14:15

Mike Seymour · Accepted Answer · 2012-07-05 15:18:52Z

7

Check the prototype in your .hpp file. It's probably declared as

void AddBenchNode(ref_ptr<Group> root ,ref_ptr<Node> benches, bool setAttitude, 
                  float scale_x, float scale_y, float scale_z, int positionx, 
                  int positiony, int positionz);

EDIT: The prototype in the header should be

void AddBenchNode(ref_ptr<Group> root ,ref_ptr<Node> benches, bool setAttitude = false, float scale_x =.15, float scale_y =15, float scale_z = 15, int positionx = 250, int positiony = 100, int positionz =0 );

And your cpp file should then only have

void AddBenchNode(ref_ptr<Group> root ,ref_ptr<Node> benches, bool setAttitude, float scale_x, float scale_y, float scale_z, int positionx, int positiony, int positionz)
{

}

That is, the default parameters are in the prototype, not in the actual definition.

edited Jul 5, 2012 at 15:18

Mike Seymour

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answered Jul 5, 2012 at 14:20

Wernsey

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4 Comments

user272671 Over a year ago

This is the prototype void AddBenchNode(osg::ref_ptr<osg::Group>,osg::ref_ptr<osg::Node>, bool, float, float, float, int, int, int );

user272671 Over a year ago

My question is why I am not able to call the same function this way AddBenchNode(root, benches, false, 250);

molbdnilo Over a year ago

+1, but I think your first line should say "declared" and the last line should say "definition". Just picking nits ;-)

user272671 Over a year ago

Thank you. You are right, I had it the other way around. Thank you!

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