A C++ STL iterator with strictly read-only access.
const_iterator is an stl iterator with strictly read-only access.
Questions tagged [const-iterator]
161 questions
361
votes
8 answers
How to implement an STL-style iterator and avoid common pitfalls?
I made a collection for which I want to provide an STL-style, random-access iterator. I was searching around for an example implementation of an iterator but I didn't find any. I know about the need for const overloads of [] and * operators. What…
Tamás Szelei
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303
votes
9 answers
How to correctly implement custom iterators and const_iterators?
I have a custom container class for which I'd like to write the iterator and const_iterator classes.
I never did this before and I failed to find an appropriate how-to. What are the guidelines regarding iterator creation, and what should I be aware…
ereOn
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219
votes
7 answers
What is the reason behind cbegin/cend?
I wonder why cbegin and cend were introduced in C++11?
What are cases when calling these methods makes a difference from const overloads of begin and end?
Andriy
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153
votes
3 answers
what is the difference between const_iterator and iterator?
What is difference between these two regarding implementation inside STL.
what is the difference regarding performance?
I guess when we are traversing the vector in "read only wise", we prefer const_iterator, right?
Thank you.
user658266
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57
votes
10 answers
How to remove constness of const_iterator?
As an extension to this question Are const_iterators faster?, I have another question on const_iterators. How to remove constness of a const_iterator?
Though iterators are generalised form of pointers but still const_iterator and iterators are two…
aJ.
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39
votes
11 answers
Are const_iterators faster?
Our coding guidelines prefer const_iterator, because they are a little faster compared to a normal iterator. It seems like the compiler optimizes the code when you use const_iterator.
Is this really correct? If yes, what really happens internally…
aJ.
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36
votes
3 answers
Is comparison of const_iterator with iterator well-defined?
Consider the following code:
#include
#include
int main()
{
std::vector vec{1,2,3,5};
for(auto it=vec.cbegin();it!=vec.cend();++it)
{
std::cout << *it;
// A typo: end instead of cend
…
Ruslan
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29
votes
1 answer
New std::map::erase() signature C++17
According to this answer, an iterator must be implicitly convertible to const_iterator. Since that is true, as we can see happening in insert_or_assign(), then why in C++17 was a new signature added to std::map::erase()?
In C++11, we have iterator…
João Paulo
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27
votes
6 answers
Should I prefer iterators over const_iterators?
Someone here recently brought up the article from Scott Meyers that says:
Prefer iterators over const_iterators (pdf link).
Someone else was commenting that the article is probably outdated. I'm wondering what your opinions are?
Here is mine: One…
Frank
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26
votes
2 answers
C++ iterator to const_iterator
How do I acquire a const_iterator (of some container class) from an iterator (of that container class) in C++? What about a const_iterator from an insert_iterator? The resulting iterator should point at the same spot as the original does.
Thomas Eding
- 35,312
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21
votes
2 answers
const_iterator and constness of const_iterator::value_type
Why in STL
std::iterator_traits::value_type
is the same type as
std::iterator_traits::value_type
Why it is designed like that? Shouldn't the first be const T and the second only T? How are you supposed to take the underlying const…
Sogartar
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17
votes
2 answers
Why const_iterator could be used with std::map::erase
I was under the impression one cant use erase on a const iterator. Check this code.
Why does the below code compile (C++11, gcc)?
long getMax(const bool get_new)
{
long max_val=0;
TO now=getNow();
map&…
chrise
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14
votes
3 answers
C++ iterator and const_iterator problem for own container class
I'm writing an own container class and have run into a problem I can't get my head around. Here's the bare-bone sample that shows the problem.
It consists of a container class and two test classes: one test class using a std:vector which compiles…
BaCh
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12
votes
2 answers
Why elements can be inserted in a vector when using const_iterators
Considering the code below,
#include
#include
#include
using namespace std;
int main(){
vector value{22, 23, 25, 34, 99};
auto it = find(value.cbegin(), value.cend(), 25);
value.insert(it, 77);
…
Milo Lu
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12
votes
1 answer
In C++17, why do associative containers have an `erase` member function that takes (non-`const`) `iterator`?
See, e.g., http://en.cppreference.com/w/cpp/container/map/erase
In C++03 there were three overloads:
void erase( iterator pos );
void erase( iterator first, iterator last );
size_type erase( const key_type& key );
In C++11, the first and second…
Brian Bi
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