Python's enumerate in c++
-2
In Python , instead of
colors = ['red', 'green', 'blue', 'yellow']
for i in range(len(colors)):
print i, '--->', colors[i]
One can write
for i, color in enumerate(colors):
print i, '--->', color
Is there a similar thing in c++?
c++ enumerator
asked Dec 23 '17 at 0:20
athosathos
2,18213062
add a comment |
-2
In Python , instead of
colors = ['red', 'green', 'blue', 'yellow']
for i in range(len(colors)):
print i, '--->', colors[i]
One can write
for i, color in enumerate(colors):
print i, '--->', color
Is there a similar thing in c++?
c++ enumerator
asked Dec 23 '17 at 0:20
athosathos
2,18213062
I don't think so. If you iterate over astd::vector, it just gives you the elements, not the indexes.
– Barmar
Dec 23 '17 at 0:25
Possible duplicate of What is the most effective way to get the index of an iterator of an std::vector?
– Barmar
Dec 23 '17 at 0:27
add a comment |
-2
-2
-2
In Python , instead of
colors = ['red', 'green', 'blue', 'yellow']
for i in range(len(colors)):
print i, '--->', colors[i]
One can write
for i, color in enumerate(colors):
print i, '--->', color
Is there a similar thing in c++?
c++ enumerator
asked Dec 23 '17 at 0:20
athosathos
2,18213062
In Python , instead of
colors = ['red', 'green', 'blue', 'yellow']
for i in range(len(colors)):
print i, '--->', colors[i]
One can write
for i, color in enumerate(colors):
print i, '--->', color
Is there a similar thing in c++?
c++ enumerator
c++ enumerator
asked Dec 23 '17 at 0:20
athosathos
2,18213062
asked Dec 23 '17 at 0:20
athosathos
2,18213062
asked Dec 23 '17 at 0:20
athosathos
2,18213062
asked Dec 23 '17 at 0:20
athosathos
2,18213062
asked Dec 23 '17 at 0:20
athosathos
2,18213062
2,18213062
I don't think so. If you iterate over astd::vector, it just gives you the elements, not the indexes.
– Barmar
Dec 23 '17 at 0:25
Possible duplicate of What is the most effective way to get the index of an iterator of an std::vector?
– Barmar
Dec 23 '17 at 0:27
add a comment |
I don't think so. If you iterate over astd::vector, it just gives you the elements, not the indexes.
– Barmar
Dec 23 '17 at 0:25
Possible duplicate of What is the most effective way to get the index of an iterator of an std::vector?
– Barmar
Dec 23 '17 at 0:27
I don't think so. If you iterate over a
std::vector, it just gives you the elements, not the indexes.– Barmar
Dec 23 '17 at 0:25
I don't think so. If you iterate over a
std::vector, it just gives you the elements, not the indexes.– Barmar
Dec 23 '17 at 0:25
Possible duplicate of What is the most effective way to get the index of an iterator of an std::vector?
– Barmar
Dec 23 '17 at 0:27
Possible duplicate of What is the most effective way to get the index of an iterator of an std::vector?
– Barmar
Dec 23 '17 at 0:27
add a comment |
3 Answers
3
active
oldest
votes
1
You can actually implement something similar in c++17.
Here is a sketch(c++-ish pseudocode), I use values everywhere and they should be replaced by appropriate references/forwarding, also you should fix how you get types (use iterator_traits), may be support unknown size, may be implement proper iterator interface etc
template <typename T>
struct EnumeratedIterator {
size_t index;
T iterator;
void operator++() {
++iterator;
}
std::pair<size_t, T>() {
return {index, *iterator};
}
bool operator !=(EnumeratedIterator o) {
return iterator != o.iterator;
}
}
template <typename T>
struct Enumerated {
T collection;
EnumeratedIterator<typename T::iterator> begin() {
return {0, collection.begin()};
}
EnumeratedIterator<typename T::iterator> end() {
return {collection.size(), collection.end()};
}
}
auto enumerate(T col) {
return Enumerated<T>(col);
}
and then use it like
for (auto [index, color] : enumerate(vector<int>{5, 7, 10})) {
assert(index < color);
}
answered Dec 23 '17 at 0:51
RiaDRiaD
32.8k955102
add a comment |
1
Boost provides an adaptor which allows to do something similiar:
http://www.boost.org/doc/libs/1_63_0/libs/range/doc/html/range/reference/adaptors/reference/indexed.html
The following code is taken from the link above
#include <boost/range/adaptor/indexed.hpp>
#include <boost/assign.hpp>
#include <iterator>
#include <iostream>
#include <vector>
int main(int argc, const char* argv)
{
using namespace boost::assign;
using namespace boost::adaptors;
std::vector<int> input;
input += 10,20,30,40,50,60,70,80,90;
for (const auto& element : input | indexed(0))
{
std::cout << "Element = " << element.value()
<< " Index = " << element.index()
<< std::endl;
}
return 0;
}
answered Dec 23 '17 at 0:28
OmniOmni
716411
3
Side topic, how doesinput += 10,20,30,40,50,60,70,80,90;work? I'm amazed...
– athos
Dec 23 '17 at 0:33
1
boost.org/doc/libs/1_62_0/libs/assign/doc/index.html#operator+=
– Omni
Dec 23 '17 at 0:39
add a comment |
1
Maybe you can emulate it like this:
int i = 0;
for (auto color : { "red", "green", "blue", "yellow" })
std::cout << i++ << "--->" << color << std::endl;
answered Dec 23 '17 at 0:38
Killzone KidKillzone Kid
4,8453728
Can't setitoconstis my only complain...
– athos
Dec 23 '17 at 0:40
and now run this function two times and you'll get 4,5,6,7 instead of indexes
– RiaD
Dec 23 '17 at 0:44
@RiaD this is not a function
– Killzone Kid
Dec 23 '17 at 0:55
1
@KillzoneKid No, but this code must be put inside a function somewhere, and when it does, thestaticwill cause issues on repeated invocations of the function. Just remove thestatickeyword and move youriinitialisation to before the loop.
– hnefatl
Dec 23 '17 at 0:56
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
1
You can actually implement something similar in c++17.
Here is a sketch(c++-ish pseudocode), I use values everywhere and they should be replaced by appropriate references/forwarding, also you should fix how you get types (use iterator_traits), may be support unknown size, may be implement proper iterator interface etc
template <typename T>
struct EnumeratedIterator {
size_t index;
T iterator;
void operator++() {
++iterator;
}
std::pair<size_t, T>() {
return {index, *iterator};
}
bool operator !=(EnumeratedIterator o) {
return iterator != o.iterator;
}
}
template <typename T>
struct Enumerated {
T collection;
EnumeratedIterator<typename T::iterator> begin() {
return {0, collection.begin()};
}
EnumeratedIterator<typename T::iterator> end() {
return {collection.size(), collection.end()};
}
}
auto enumerate(T col) {
return Enumerated<T>(col);
}
and then use it like
for (auto [index, color] : enumerate(vector<int>{5, 7, 10})) {
assert(index < color);
}
answered Dec 23 '17 at 0:51
RiaDRiaD
32.8k955102
add a comment |
1
You can actually implement something similar in c++17.
Here is a sketch(c++-ish pseudocode), I use values everywhere and they should be replaced by appropriate references/forwarding, also you should fix how you get types (use iterator_traits), may be support unknown size, may be implement proper iterator interface etc
template <typename T>
struct EnumeratedIterator {
size_t index;
T iterator;
void operator++() {
++iterator;
}
std::pair<size_t, T>() {
return {index, *iterator};
}
bool operator !=(EnumeratedIterator o) {
return iterator != o.iterator;
}
}
template <typename T>
struct Enumerated {
T collection;
EnumeratedIterator<typename T::iterator> begin() {
return {0, collection.begin()};
}
EnumeratedIterator<typename T::iterator> end() {
return {collection.size(), collection.end()};
}
}
auto enumerate(T col) {
return Enumerated<T>(col);
}
and then use it like
for (auto [index, color] : enumerate(vector<int>{5, 7, 10})) {
assert(index < color);
}
answered Dec 23 '17 at 0:51
RiaDRiaD
32.8k955102
add a comment |
1
1
1
You can actually implement something similar in c++17.
Here is a sketch(c++-ish pseudocode), I use values everywhere and they should be replaced by appropriate references/forwarding, also you should fix how you get types (use iterator_traits), may be support unknown size, may be implement proper iterator interface etc
template <typename T>
struct EnumeratedIterator {
size_t index;
T iterator;
void operator++() {
++iterator;
}
std::pair<size_t, T>() {
return {index, *iterator};
}
bool operator !=(EnumeratedIterator o) {
return iterator != o.iterator;
}
}
template <typename T>
struct Enumerated {
T collection;
EnumeratedIterator<typename T::iterator> begin() {
return {0, collection.begin()};
}
EnumeratedIterator<typename T::iterator> end() {
return {collection.size(), collection.end()};
}
}
auto enumerate(T col) {
return Enumerated<T>(col);
}
and then use it like
for (auto [index, color] : enumerate(vector<int>{5, 7, 10})) {
assert(index < color);
}
answered Dec 23 '17 at 0:51
RiaDRiaD
32.8k955102
You can actually implement something similar in c++17.
Here is a sketch(c++-ish pseudocode), I use values everywhere and they should be replaced by appropriate references/forwarding, also you should fix how you get types (use iterator_traits), may be support unknown size, may be implement proper iterator interface etc
template <typename T>
struct EnumeratedIterator {
size_t index;
T iterator;
void operator++() {
++iterator;
}
std::pair<size_t, T>() {
return {index, *iterator};
}
bool operator !=(EnumeratedIterator o) {
return iterator != o.iterator;
}
}
template <typename T>
struct Enumerated {
T collection;
EnumeratedIterator<typename T::iterator> begin() {
return {0, collection.begin()};
}
EnumeratedIterator<typename T::iterator> end() {
return {collection.size(), collection.end()};
}
}
auto enumerate(T col) {
return Enumerated<T>(col);
}
and then use it like
for (auto [index, color] : enumerate(vector<int>{5, 7, 10})) {
assert(index < color);
}
answered Dec 23 '17 at 0:51
RiaDRiaD
32.8k955102
edited Nov 25 '18 at 6:06
answered Dec 23 '17 at 0:51
RiaDRiaD
32.8k955102
answered Dec 23 '17 at 0:51
RiaDRiaD
32.8k955102
answered Dec 23 '17 at 0:51
RiaDRiaD
32.8k955102
32.8k955102
add a comment |
add a comment |
1
Boost provides an adaptor which allows to do something similiar:
http://www.boost.org/doc/libs/1_63_0/libs/range/doc/html/range/reference/adaptors/reference/indexed.html
The following code is taken from the link above
#include <boost/range/adaptor/indexed.hpp>
#include <boost/assign.hpp>
#include <iterator>
#include <iostream>
#include <vector>
int main(int argc, const char* argv)
{
using namespace boost::assign;
using namespace boost::adaptors;
std::vector<int> input;
input += 10,20,30,40,50,60,70,80,90;
for (const auto& element : input | indexed(0))
{
std::cout << "Element = " << element.value()
<< " Index = " << element.index()
<< std::endl;
}
return 0;
}
answered Dec 23 '17 at 0:28
OmniOmni
716411
3
Side topic, how doesinput += 10,20,30,40,50,60,70,80,90;work? I'm amazed...
– athos
Dec 23 '17 at 0:33
1
boost.org/doc/libs/1_62_0/libs/assign/doc/index.html#operator+=
– Omni
Dec 23 '17 at 0:39
add a comment |
1
Boost provides an adaptor which allows to do something similiar:
http://www.boost.org/doc/libs/1_63_0/libs/range/doc/html/range/reference/adaptors/reference/indexed.html
The following code is taken from the link above
#include <boost/range/adaptor/indexed.hpp>
#include <boost/assign.hpp>
#include <iterator>
#include <iostream>
#include <vector>
int main(int argc, const char* argv)
{
using namespace boost::assign;
using namespace boost::adaptors;
std::vector<int> input;
input += 10,20,30,40,50,60,70,80,90;
for (const auto& element : input | indexed(0))
{
std::cout << "Element = " << element.value()
<< " Index = " << element.index()
<< std::endl;
}
return 0;
}
answered Dec 23 '17 at 0:28
OmniOmni
716411
3
Side topic, how doesinput += 10,20,30,40,50,60,70,80,90;work? I'm amazed...
– athos
Dec 23 '17 at 0:33
1
boost.org/doc/libs/1_62_0/libs/assign/doc/index.html#operator+=
– Omni
Dec 23 '17 at 0:39
add a comment |
1
1
1
Boost provides an adaptor which allows to do something similiar:
http://www.boost.org/doc/libs/1_63_0/libs/range/doc/html/range/reference/adaptors/reference/indexed.html
The following code is taken from the link above
#include <boost/range/adaptor/indexed.hpp>
#include <boost/assign.hpp>
#include <iterator>
#include <iostream>
#include <vector>
int main(int argc, const char* argv)
{
using namespace boost::assign;
using namespace boost::adaptors;
std::vector<int> input;
input += 10,20,30,40,50,60,70,80,90;
for (const auto& element : input | indexed(0))
{
std::cout << "Element = " << element.value()
<< " Index = " << element.index()
<< std::endl;
}
return 0;
}
answered Dec 23 '17 at 0:28
OmniOmni
716411
Boost provides an adaptor which allows to do something similiar:
http://www.boost.org/doc/libs/1_63_0/libs/range/doc/html/range/reference/adaptors/reference/indexed.html
The following code is taken from the link above
#include <boost/range/adaptor/indexed.hpp>
#include <boost/assign.hpp>
#include <iterator>
#include <iostream>
#include <vector>
int main(int argc, const char* argv)
{
using namespace boost::assign;
using namespace boost::adaptors;
std::vector<int> input;
input += 10,20,30,40,50,60,70,80,90;
for (const auto& element : input | indexed(0))
{
std::cout << "Element = " << element.value()
<< " Index = " << element.index()
<< std::endl;
}
return 0;
}
answered Dec 23 '17 at 0:28
OmniOmni
716411
edited Dec 23 '17 at 0:37
answered Dec 23 '17 at 0:28
OmniOmni
716411
answered Dec 23 '17 at 0:28
OmniOmni
716411
answered Dec 23 '17 at 0:28
OmniOmni
716411
716411
3
Side topic, how doesinput += 10,20,30,40,50,60,70,80,90;work? I'm amazed...
– athos
Dec 23 '17 at 0:33
1
boost.org/doc/libs/1_62_0/libs/assign/doc/index.html#operator+=
– Omni
Dec 23 '17 at 0:39
add a comment |
3
Side topic, how doesinput += 10,20,30,40,50,60,70,80,90;work? I'm amazed...
– athos
Dec 23 '17 at 0:33
1
boost.org/doc/libs/1_62_0/libs/assign/doc/index.html#operator+=
– Omni
Dec 23 '17 at 0:39
3
3
Side topic, how does
input += 10,20,30,40,50,60,70,80,90; work? I'm amazed...– athos
Dec 23 '17 at 0:33
Side topic, how does
input += 10,20,30,40,50,60,70,80,90; work? I'm amazed...– athos
Dec 23 '17 at 0:33
1
1
boost.org/doc/libs/1_62_0/libs/assign/doc/index.html#operator+=
– Omni
Dec 23 '17 at 0:39
boost.org/doc/libs/1_62_0/libs/assign/doc/index.html#operator+=
– Omni
Dec 23 '17 at 0:39
add a comment |
1
Maybe you can emulate it like this:
int i = 0;
for (auto color : { "red", "green", "blue", "yellow" })
std::cout << i++ << "--->" << color << std::endl;
answered Dec 23 '17 at 0:38
Killzone KidKillzone Kid
4,8453728
Can't setitoconstis my only complain...
– athos
Dec 23 '17 at 0:40
and now run this function two times and you'll get 4,5,6,7 instead of indexes
– RiaD
Dec 23 '17 at 0:44
@RiaD this is not a function
– Killzone Kid
Dec 23 '17 at 0:55
1
@KillzoneKid No, but this code must be put inside a function somewhere, and when it does, thestaticwill cause issues on repeated invocations of the function. Just remove thestatickeyword and move youriinitialisation to before the loop.
– hnefatl
Dec 23 '17 at 0:56
add a comment |
1
Maybe you can emulate it like this:
int i = 0;
for (auto color : { "red", "green", "blue", "yellow" })
std::cout << i++ << "--->" << color << std::endl;
answered Dec 23 '17 at 0:38
Killzone KidKillzone Kid
4,8453728
Can't setitoconstis my only complain...
– athos
Dec 23 '17 at 0:40
and now run this function two times and you'll get 4,5,6,7 instead of indexes
– RiaD
Dec 23 '17 at 0:44
@RiaD this is not a function
– Killzone Kid
Dec 23 '17 at 0:55
1
@KillzoneKid No, but this code must be put inside a function somewhere, and when it does, thestaticwill cause issues on repeated invocations of the function. Just remove thestatickeyword and move youriinitialisation to before the loop.
– hnefatl
Dec 23 '17 at 0:56
add a comment |
1
1
1
Maybe you can emulate it like this:
int i = 0;
for (auto color : { "red", "green", "blue", "yellow" })
std::cout << i++ << "--->" << color << std::endl;
answered Dec 23 '17 at 0:38
Killzone KidKillzone Kid
4,8453728
Maybe you can emulate it like this:
int i = 0;
for (auto color : { "red", "green", "blue", "yellow" })
std::cout << i++ << "--->" << color << std::endl;
answered Dec 23 '17 at 0:38
Killzone KidKillzone Kid
4,8453728
edited Dec 23 '17 at 1:10
answered Dec 23 '17 at 0:38
Killzone KidKillzone Kid
4,8453728
answered Dec 23 '17 at 0:38
Killzone KidKillzone Kid
4,8453728
answered Dec 23 '17 at 0:38
Killzone KidKillzone Kid
4,8453728
4,8453728
Can't setitoconstis my only complain...
– athos
Dec 23 '17 at 0:40
and now run this function two times and you'll get 4,5,6,7 instead of indexes
– RiaD
Dec 23 '17 at 0:44
@RiaD this is not a function
– Killzone Kid
Dec 23 '17 at 0:55
1
@KillzoneKid No, but this code must be put inside a function somewhere, and when it does, thestaticwill cause issues on repeated invocations of the function. Just remove thestatickeyword and move youriinitialisation to before the loop.
– hnefatl
Dec 23 '17 at 0:56
add a comment |
Can't setitoconstis my only complain...
– athos
Dec 23 '17 at 0:40
and now run this function two times and you'll get 4,5,6,7 instead of indexes
– RiaD
Dec 23 '17 at 0:44
@RiaD this is not a function
– Killzone Kid
Dec 23 '17 at 0:55
1
@KillzoneKid No, but this code must be put inside a function somewhere, and when it does, thestaticwill cause issues on repeated invocations of the function. Just remove thestatickeyword and move youriinitialisation to before the loop.
– hnefatl
Dec 23 '17 at 0:56
Can't set
i to const is my only complain...– athos
Dec 23 '17 at 0:40
Can't set
i to const is my only complain...– athos
Dec 23 '17 at 0:40
and now run this function two times and you'll get 4,5,6,7 instead of indexes
– RiaD
Dec 23 '17 at 0:44
and now run this function two times and you'll get 4,5,6,7 instead of indexes
– RiaD
Dec 23 '17 at 0:44
@RiaD this is not a function
– Killzone Kid
Dec 23 '17 at 0:55
@RiaD this is not a function
– Killzone Kid
Dec 23 '17 at 0:55
1
1
@KillzoneKid No, but this code must be put inside a function somewhere, and when it does, the
static will cause issues on repeated invocations of the function. Just remove the static keyword and move your i initialisation to before the loop.– hnefatl
Dec 23 '17 at 0:56
@KillzoneKid No, but this code must be put inside a function somewhere, and when it does, the
static will cause issues on repeated invocations of the function. Just remove the static keyword and move your i initialisation to before the loop.– hnefatl
Dec 23 '17 at 0:56
add a comment |
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I don't think so. If you iterate over a
std::vector, it just gives you the elements, not the indexes.– Barmar
Dec 23 '17 at 0:25
Possible duplicate of What is the most effective way to get the index of an iterator of an std::vector?
– Barmar
Dec 23 '17 at 0:27