std Questions
3
EDIT: total re-edit because the original was becoming an unstructured mess :) Thanks for everyone's input so far; I hope I worked it into the text below.
Question
I'm in search for a lazily-creat...
Nedranedrah asked 17/9, 2015 at 21:29
5
Solved
std::unordered_map<std::string, bool> str_bool_map = {
{"a", true},
{"b", false},
{"c", true}
};
can we use std::any_of on this map to see any of its values is false? Or any of its key i...
2
Solved
unsigned int Tick = GetTickCount();
This code is running only on Windows, but I want to use the C++ Standard library so it can run elsewhere.
I searched std::chrono, but I can't find a function ...
Diminution asked 25/7, 2014 at 13:57
8
I'm trying to read a line using the following code:
while(fscanf(f, "%[^\n\r]s", cLine) != EOF )
{
/* do something with cLine */
}
But somehow I get only the first line every time. Is this a ba...
2
The "four basic kinds" of C++ sequence containers
(vector, forward_list, list, and deque)
all have an assign method. For example, std::vector has
(quoting cppreference.com):
void as...
2
Solved
I know that it makes perfect sense to define e.g. move constructor as noexcept (if possible) and I think I understand the effect of that.
But I have never seen a similar discussion about operator&l...
Massingill asked 10/7 at 11:44
1
Solved
I've reduced my code to the following example, which fails -O3 C++20 compilation on my g++ (x64 12.3) as well as apparently 14.1 when using godbolt:
Again according to godbolt, clang works without ...
2
Solved
I would like to know what's the best practice to remove an element from a vector in C++.
I have seen many times people using std::remove to find and delete the element, and then using erase to rem...
1
I know about this question, but mine is a bit different.
Why does rehash have quadratic complexity, but operator [] (which can call rehash) has linear complexity in worst case?
Sorry, but I don't h...
Hep asked 9/2 at 18:40
19
Solved
How do I replace part of a string with another string using the standard C++ libraries?
QString s("hello $name"); // Example using Qt.
s.replace("$name", "Somename");
...
0
When I allocate large space with std::vector it takes significant time because std::vector default-initializes the objects in it.
I see that a long time ago people discussed the topic in the ...
Desultory asked 21/3 at 22:8
4
Solved
I wanted to do this
#include <vector>
#include <span>
struct S
{
std::vector<int> v;
void set(std::span<int> _v)
{
v = _v;
}
};
But it does not compile. What are the ...
5
I am beginning with c++11, constexpr and template metaprogramming seems a nice way to save scarce ram on tiny microcontroler.
Is there a way to write a template to flatten a list of constexpr arr...
11
Solved
I'm trying to declare a priority_queue of nodes, using bool Compare(Node a, Node b) as the comparator function (which is outside the node class).
What I currently have is:
priority_queue<Node,...
Partner asked 19/4, 2013 at 18:33
6
How do I write a template function that operates on a arbitrary container of a arbitrary type? For example how do I generalize this dummy function
template <typename Element>
void print_size...
2
Solved
I need to construct a multi-string (REG_MULTI_SZ) in C++ from a list of values represented in a std::vector<std::wstring>.
This is what first came to mind but was of course incorrect:
std::ws...
Boyhood asked 24/1 at 15:41
3
I would like to swap two arrays of ints of some fixed size.
Counterintuitively, the following does not compile because no matching instance of swap has been found.
#include <array>
#include &...
3
Solved
If there is a std::map<std::pair<std::string, std::string>, some_type> what is the best way to find its values?
I guess the most obvious one is to do something like this:
map.find(std::...
5
Solved
I tried to use the operator[] access the element in a const map, but this method failed. I also tried to use at() to do the same thing. It worked this time. However, I could not find any reference ...
Volkan asked 27/2, 2011 at 17:17
2
I have a variable called last_timestamp_ which is declared as follows:
using TimePoint = std::chrono::time_point<std::chrono::system_clock, std::chrono::duration<double>> TimePoint last...
5
Solved
I have a string like this:
std::string string1 = "xjdfhfakdjs%54k34k.-jk34";
I need to get only ""xjdfhfakdjs", but the string is dynamic, not hardcoded so I don't know what is it, the length et...
Nimble asked 1/5, 2012 at 1:11
1
Solved
In libstdc++ and libc++ the internal nodes for lists (e.g. list and forward_list) and other trees are constructed in (at least) two parts: a node base class; and the node class itself. For example,...
Kerley asked 27/5, 2020 at 8:58
2
Solved
If I want to write a function summing two std::array, I would do something like:
template<class T, std::size_t N>
auto sum(const std::array<T, N>& a, const std::array<T, N>&am...
2
Solved
I wanted to use the parallel version of std::sort where I can specify an execution policy like std::execution::par_unseq.
I'm currently using clang++-10 and g++ 7.5.0 under Ubuntu Linux, but both d...
4
Solved
I'm trying to figure out a nice way to find the index of a certain object in a vector - by comparing a string to a member field in the object.
Like this:
find(vector.begin(), vector.end(), [obje...
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