CODEWITHSUNDEEP
c++
demorge
demorge

Reputation: 1117

Initializing table with variable argument list

In my code I want to be able to do

Table<double> tbl;
tbl.Create(2, 2, 1.0, 2.0, 3.0, 4.0);

and via the constructor too

Table<double> tbl(2, 2, 1.0, 2.0, 3.0, 4.0);

From my experience the use of ellipses (...) leads to several hard to trace bugs, so I've come up with the following to initialize my table:

void Create(size_t rows, size_t columns, T val0)
{
    ASSERT(rows * columns == 1);
    Create(rows, columns);
    _data[0] = val0;
}

void Create(size_t rows, size_t columns, T val0, T val1)
{
    ASSERT(rows * columns == 2);
    Create(rows, columns);
    _data[0] = val0;
    _data[1] = val1;
}

void Create(size_t rows, size_t columns, T val0, T val1, T val2)
{
    ASSERT(rows * columns == 3);
    Create(rows, columns);
    _data[0] = val0;
    _data[1] = val1;
    _data[2] = val2;
}

I think you get the idea. However, this becomes rather annoying if I want functions for say up to 50 elements. Not to mention the fact I'll have to write all these constructors too. Isn't there another way to handle this more elegantly?

EDIT: Maybe I should explain why I don't want to use ellipses (...) in this case. Let's consider the following code:

Table<double> tbl(2, 2, 1.5, 2.1, 3, 4.5);

The compiler interprets the 5th argument as type int and this is clearly not intended.

Upvotes: 0

Views: 191

Answers (1)

Kerrek SB
Kerrek SB

Reputation: 477100

Variadic templates and initializer lists might work:

struct Table
{
    std::vector<double> data;

    template <typename ...Args>
    Table(Args &&... args)
    : data({std::forward<Args>(args)...})
    {  }
};

Upvotes: 3

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