Question

I have a point3 struct that takes 3 floats x, y, z (3-D space coordinates).

I’m trying to write a function that translates the x, y, z values of each element in a list of points.

I’m new to C++ so I don’t think I wrote the iterator correctly, can anyone help clarify how to iterate down a list and modify components of each element in the list?

I looked at this post C++ How to loop through a list of structs and access their properties and thought this answered my problem, but the solution didn’t work.

Here is my code:

//Translates the face by dx, dy, dz coordinates
list<point3> translateFace(list<point3> lop, float dx, float dy, float dz)
{
    list<point3>::iterator iter;

    for (iter = lop.begin() ; iter != lop.end(); iter++){
        iter->x - dx;
        iter->y - dy;
        iter->z - dz;
    }
   return lop;
}

I also tried the solution suggested in the link above, still didn’t work. Should return lop be inside or outside the for loop? Should I be returning something other than lop?

for (iter = lop.begin() ; iter != lop.end(); iter++){
    (*iter).x - dx;
    (*iter).y - dy;
    (*iter).z - dz;
    }
return lop;

Answer 1

It appears to me that you’re not actually storing the results of your calculation:

for (iter = lop.begin() ; iter != lop.end(); iter++){
    iter->x - dx;
    iter->y - dy;
    iter->z - dz;
}

Try this:

for (iter = lop.begin() ; iter != lop.end(); iter++){
    iter->x -= dx;
    iter->y -= dy;
    iter->z -= dz;
}

I would hope most compilers would throw a warning about an unused calculation like this — turn up the warning level on your compiler if you can.