Unresolved overloaded function type - array overloading in C ++
So, I have a vector class that looks a bit like it (most of the methods have been removed for clarity):
class D3Vector {
private:
double _values[3];
public:
const double& operator[](const int index) const;
double& operator[](const int index);
};
double& D3Vector::operator[](const int index) {
assert(index >= 0 && index < 3);
return _values[index];
}
const double& D3Vector::operator[](const int index) const {
assert(index >= 0 && index < 3);
return _values[index];
}
And at some point in my code, I call this array index overload like this:
void func(D3Vector centre, double radius) {
double limits[6];
int i;
for (i = 0; i < 3; i++) {
// both these lines cause the error...
limits[i] = centre[i] - radius;
limits[i + 3] = centre[i] + radius;
}
...
}
but I am getting this error at compile time:
error: invalid types '<unresolved overloaded function type>[int]' for array subscript
Now I've fumbled with the overload function signatures, adding and removing reference characters, adding and removing a constant, but I'm really just guessing here.
What is a sane way to write overloads of array index operators for a vector class for real numbers like this, which allows us to do simple things like:
instance[i] = 5.7;
and
new_value = instance[j] + 17.3;
?
EDIT : Complete class specification, as requested:
class D3Vector {
private:
double _values[3];
public:
// constructors - no args inits to 0.0
D3Vector();
D3Vector(const double x, const double y, const double z);
// binary + and -:
D3Vector operator+(const D3Vector& right);
D3Vector operator-(const D3Vector& right);
// unary -, reverses sign of components:
D3Vector operator-();
// binary *, scales components.
D3Vector operator*(const double scale);
// the same, as self-assignment operations:
D3Vector& operator+=(const D3Vector& right);
D3Vector& operator-=(const D3Vector& right);
D3Vector& operator*=(const double scale);
// subscript operator, for member data access.
const double& operator[](const int index) const;
double& operator[](const int index);
// dot product:
double dot(D3Vector& right);
// cross product:
D3Vector cross(D3Vector& right);
// shortcut to vector length:
double mod();
// faster way of getting length squared:
double mod_squared();
};
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As commenters point out, this error appears when you try to call a function using parentheses []
instead of parentheses ()
. This is exactly what is happening here and was not obvious because I was simplifying the example code.
In the question, I'm posting an example function called func
- it was actually the constructor of an inherited class (hence, instead of posting all the code, I've simplified it.)
The base class contains everything we need to know:
class D3Shape {
protected:
double l[6];
virtual void initilise_limits() = 0;
public:
virtual bool contains(D3Vector point) = 0;
vector<double> limits();
};
i.e. I was confused l
, the private member variable storing double[6]
I was looking for with limits()
, a function to retrieve them in the container std::vector<double>
. This was complicated by the fact that I (successfully) used my real class with an index-overloaded class on the same line, which confused me! The compiler error "column number" in the file actually pointed to the first character after =
, which mutated the waters even more.
Many thanks to everyone who commented.
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