CODEWITHSUNDEEP
c++templatesmultidimensional-array
Franz Kafka
Franz Kafka

Reputation: 87

How to do a print version of 3D objects with templates? (c++)

I guess you have seen this particular function:

template<typename T> void print(const T& cont){
    for (auto &i: cont)
        std::cout << i << " ";
    std::cout << std::endl;
}

It print's almost all type of containers like std::list. Now i wanna create one that prints (as example) 3D std::vector, look at this fantasy:

template<typename T1, typename T2> void print(const T1<T2>&);

But of course this is not how templates work. How to do that? And not less important: is any difference of doing that in c++17 and pre-c++17?

Upvotes: 2

Views: 82

Answers (1)

cigien
cigien

Reputation: 60238

You can write the following template overloads, one that prints a 1-D range, and one that prints an N-D range by printing each nested (N-1)D range in a loop:

template<template<typename...> class Range,  
      // ^                         ^ 
      // Note the template template parameter
         typename T> 
void print(Range<T> const & cont)  // #1
{
    for (auto const & i : cont)
        std::cout << i << " ";    // print 1-D range
    std::cout << std::endl;
}

template<template<typename...> class RangeOut, 
         template<typename...> class RangeIn, 
         typename T> 
void print(RangeOut<RangeIn<T>> const & cont) // #2
{
    for (auto const &i: cont)
        print(i);              // call print overload:
                               // calls #1 if RangeIn is 1-D range
                               // calls #2 otherwise 
    std::cout << std::endl;
}

Now you can print containers (ranges) of arbitrary dimensionality, and composed of heterogenous types, e.g:

std::vector<std::list<std::vector<int>>> vlv{{{1,2}, {3}} ,{{4,5}, {6}}};
print(vlv); // ok

Here's a demo.

Upvotes: 5

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