1,514 questions
1
vote
2
answers
136
views
Are the map/multimap iterators interchangeable?
In the code below I'm defining a map and a multimap. Then I'm defining four iterators assigning them values from these containers:
std::map<int, double> m;
std::multimap<int, double> mm;
...
- 6,630
2
votes
2
answers
131
views
Structured binding for std::views::enumerate of std::map [duplicate]
I'm trying to do something like this:
const std::map<char, int> histogram{
{'A', 2},
{'D', 1},
{'M', 1},
};
for (const auto& [index, key, value] : std::views::enumerate(...
- 5,533
0
votes
1
answer
174
views
Removing an element from a map of vectors
std::map<unsigned long, std::vector<Foo*> > fKeys = myObject->GetFoo();
for (auto it = fKeys.begin(); it != fKeys.end() && !found; ++it)
for (auto it1 = 0; it1 < (*it)....
- 6,453
0
votes
1
answer
149
views
How to give a hint to std::map::lower_bound?
I want to give hints to std::map::lower_bound.
Why isn't it even allowed?
Suppose we need to implement something like:
static constexpr int TOTAL_SIZE = 1'000'000;
std::map<int, std::string> map{...
- 21
3
votes
1
answer
116
views
Maximum size of static local container in C++
To avoid reporting too many errors repeatedly, I use the std::map container to cache the error code and corresponding channel number, on the other hand, for the same error occurred on the same channel,...
- 429
2
votes
3
answers
218
views
Is std::map::operator[] thread-safe if it doesn't insert?
We insert some keys into a std::map in a single thread.
Then in multiple threads, we get values using operator[] for some keys; these keys are guaranteed to have been inserted in the first step. (No ...
- 742
2
votes
2
answers
84
views
How to use std::map::emplace to add a default constructed value when it is not movable
This compiles:
#include <map>
struct S {
int val = 0;
S() = default;
S(S&&) = default;
};
int main() {
std::map<int, S> values;
values.emplace(42, S{});
}
...
- 3,479
2
votes
1
answer
108
views
C++17 std:map w/allocator gives compile error C2338 (VS 2022)
I use std::map with a simple compare function and an allocator.
Under C++17 with a map pair of std::pair<type1, type2>, I have learned that the allocator return type is required to be std::pair&...
- 23
1
vote
1
answer
146
views
Mutable static variables in consteval contxt
I'm trying to implement a consteval lambda to compute the nth Fibonacci number. I want to create a result cache in the lambda which I can use if the result is already cached. Here's what I have up ...
- 1,086
-2
votes
1
answer
49
views
How to get reference to std::map from own class inherited from (protected) map [duplicate]
I have my own class inherited from std::map, with overtyping operator to std::map.
And if I want to use it, something is wrong (conversion to unaccessible base class):
class CMyMap : protected map&...
- 527
4
votes
1
answer
97
views
C++ std::map<std::string, AnyType> find a range of partially matching strings
I have a std::map<std::string, AnyType> with following item keys:
/abc/def/ghi
/abc/def/jkl
/abc/def/mno
/abc/pqr/ghi
/abc/pqr/stw
/abc/xyz/ghi
/abc/xyz/jkl
/abc/xyz/mno
/abc/zzz/mno
is there ...
- 1,765
2
votes
1
answer
94
views
How to pick top k elements from std::map
I have a std::map with uint32_t as the key type and a custom value type. I want to pick out the top k key value pairs from this map based on the members of the value type. To do this, I'm first ...
- 1,086
2
votes
3
answers
154
views
How to move elements from std::map to std::vector
I have a std::map which contains a bunch of key value pairs. I want move these elements into a std::vector. I tried using std::transform from <algorithm> to do this, but it doesn't work. Here's ...
- 1,086
3
votes
3
answers
163
views
How do I initialize an inplace key value pair in std::map
I want to insert key value pairs into a std::map with uint32_t as the key type and a custom type for values. Based on the documentation of std::map, I wrote the following code:
#include <cstdint>...
- 1,086
-9
votes
2
answers
111
views
std::map comparison behave weirdly [closed]
Recently, I've been working on a Leetcode problem. In this problem, I tried to create a std::map<string, int> and instead of comparing the string based on alphabetical order, I want to compare ...
