Convert vector to vector ( elegant way )

Question

I would like to know if there is an elegant way or a built-in function to convert vector to vector. What I\'ve done is simp

Answer 1

There are many ways, but a standard solution is to use std::transform with a lambda using std::to_string for the conversion :

std::transform(std::begin(doubleVec),
               std::end(doubleVec), 
               std::back_inserter(doubleStr),
               [](double d) { return std::to_string(d); } 
              );

And you can wrap that in a function template to make it work with any Standard compliant container :

template
void to_string(IteratorIn first, IteratorIn last, IteratorOut out)
{
    std::transform(first, last, out,
                   [](typename std::iterator_traits::value_type d) { return std::to_string(d); } );
}

Or in C++14, with a generic lambda :

template
void to_string(IteratorIn first, IteratorIn last, IteratorOut out)
{
    std::transform(first, last, out, [](auto d) { return std::to_string(d); } );
}

And call it with any container (i.e. it works with std::list, for instance) :

to_string(std::begin(doubleVec), std::end(doubleVec), std::back_inserter(doubleStr));

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Notes :

• If you don't have a C++11 compiler, write your own to_string function template :

Example:

template
std::string my_to_string(T v)
{
    std::stringstream ss;
    ss << v;
    return ss.str();
}

And use it in a similar way :

std::transform(doubleVec.begin(),
               doubleVec.end(),
               std::back_inserter(doubleStr), 
               my_to_string );

• You should reserve() the memory in the output vector to avoid reallocations during std::transform() :

e.g. do this :

std::vector stringVec;
stringVec.reserve(v.size());   // reserve space for v.size() elements

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Live demo