range_by_example

range v3 example code

The intent of this project is to make example code for Eric Niebler's range v3 library. A host of basic information can be found on the range v3 github.

In general this code is written to c++17 so a modern C++ compiler is required. To date usage is primarily pre-release gcc-7.

Why Ranges?

Simpler more elegant code. Much detail in the standard library proposal.

Hello Ranges!

#include <range/v3/all.hpp> //get everything 
namespace rng = ranges::v3; //easy access

#include <iostream>
#include <string>
using namespace std;

int main() {

   string s { "hello" };

  //output: h e l l o
  rng::for_each( s, [](char c){ cout << c << " "; });

  cout << endl;
}

Example Conventions

In general examples will shorten code text by omitting includes and assuming the following:

#include <range/v3/all.hpp> //get everything 
namespace rng = ranges::v3; //easy access

#include <...various std library headers...>
using namespace std;

Range Library Organization

The examples are largely divided into 2 main groups -- algorithms and views.

Algorithms

for_each

Applies a function to each element of the range.

Full Example

/* output
vector:   1 2 3 4 5 6 
array:    1 2 3 4 5 6 
list:     1 2 3 4 5 6 
fwd_list: 1 2 3 4 5 6 
deque:    1 2 3 4 5 6 
*/

#include <range/v3/algorithm/for_each.hpp>   //specific includes
//...includes omitted...

auto print = [] (int i) { cout << i << " "; };

int main() {

  cout << "vector:   ";

  vector<int> v { 1, 2, 3, 4, 5, 6 };
  rng::for_each( v, print ); //1 2 3 4 5 6

  cout << endl << "array:    ";

  array<int, 6> a { 1, 2, 3, 4, 5, 6 };
  rng::for_each( a, print ); 

  cout << endl << "list:     ";
  
  list<int> ll { 1, 2, 3, 4, 5, 6 };
  rng::for_each( ll, print );

  cout << endl << "fwd_list: ";

  forward_list<int> fl { 1, 2, 3, 4, 5, 6 };
  rng::for_each( fl, print ); 

  cout << endl << "deque:    ";
  
  deque<int> d { 1, 2, 3, 4, 5, 6 };
  rng::for_each( d, print ); 

  cout << endl;
}

all_of, any_of, none_of

Tests a predicate against each element of the range returning a bool result.

Full Example

/* output
vector: 6 2 3 4 5 6 
vector any is_six: true
vector all is_six: false
vector none of is_six: false
*/

#include <range/v3/algorithm/all_of.hpp>   //specific includes
#include <range/v3/algorithm/any_of.hpp>  
#include <range/v3/algorithm/none_of.hpp>  
//...standard includes omitted...

int main() {

  cout << "vector: ";
  vector<int> v { 6, 2, 3, 4, 5, 6 };
  //...printing vector omitted...
  
  auto is_six = [](int i) -> bool { return i == 6; };

  if (rng::any_of( v, is_six ))  { 
     cout << "vector any is_six: true" << endl; 
  };
  if (!rng::all_of( v, is_six )) { 
     cout << "vector all is_six: false" << endl; 
  };
  if (!rng::none_of( v, is_six )) { 
     cout << "vector none of is_six: false" << endl; 
  };
  
}

set_union, set_intersection

Computes the union or intersection of two sets (sorted ranges).

Full Example

/* output
set s1: 1 2 3 4 5 7
set s2: 1 2 3 4 6 8
union: 1 2 3 4 5 6 7 8
intersection: 1 2 3 4
*/

#include <range/v3/algorithm/set_algorithm.hpp>
//...standard includes omitted...

namespace rng = ranges::v3;  //easy access

void output(const vector<int>& range) {
  for (auto i : range) {
    cout << i << ' ';
  }
  cout << endl;
}

int main() {

  vector<int> s1 = {1, 2, 3, 4, 5, 7};
  cout << "set s1: ";
  output(s1);

  vector<int> s2 = {1, 2, 3, 4, 6, 8};
  cout << "set s2: ";
  output(s2);

  {
    vector<int> u;
    auto it = rng::set_union(
        s1.cbegin(), s1.cend(), s2.cbegin(), s2.cend(), rng::back_inserter(u));
    cout << "union: ";
    output(u);
  }

  {
    vector<int> u;
    auto it = rng::set_intersection(
        s1.cbegin(), s1.cend(), s2.cbegin(), s2.cend(), rng::back_inserter(u));
    cout << "intersection: ";
    output(u);
  }
}

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