question about boost tuple and template

Dear all,

I have the problem:

vec1 is of the type vector<boost::tuple<int, double>>
vec2 is of the type vector<boost::tuple<int, double, double>>
vec3 is of the type vector<boost::tuple<int, double, string>>

I have to write a template with name columnViewOfTuple such that

columnViewOfTuple<0>(vec1)
columnViewOfTuple<1>(vec1)

columnViewOfTuple<0>(vec2)
columnViewOfTuple<1>(vec2)
columnViewOfTuple<2>(vec2)

columnViewOfTuple<1>(vec3)
columnViewOfTuple<2>(vec3)

returns the view of the specified column.


Can anybody give me some clues?

Quote:

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returns the view of the specified column

---

What do you mean with "the view"?

Quote:

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Originally Posted by cilu

What do you mean with "the view"?

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i mean, if vec1 ={<1, 1.1>,
<2, 2.2>,
<3, 3.3>,
<4, 4,4>}

columnViewOfTuple <0>(vec1)
returns

{1, 2, 3, 4}

If you only want read-only access with the view, you can return a copy of the data from the function.
If you want write access with the view, you'll have to return a custom class from the function that mimics the functionality of std::vector and refers internally to a column of a vector<tuple<...> >.

Hi,

Did you ever get anywhere with this? I'm have the same problem and ideally would not want to copy data...