All Questions
1,911
questions
1
vote
1
answer
70
views
How to std::accumulate chars in a string as digits using lambda?
How can I sum all digits in a string num into an integer sum using a lambda?
std::string num = "1234567891011";
int sum = accumulate(num.begin(), num.end(), 0, [](auto & a, auto & b)...
- 351
-4
votes
1
answer
28
views
Why can't I call this lambda function?
Below is a simplified version of the section of code that's causing the problem:
void reorient(C new_pos) {
// Orientate north
if (pos + 0x10 == new_pos) {
if ((orient == 0) && (Gz &...
- 459
2
votes
4
answers
192
views
C++. Accumulate binary array to integer by using custom lambda
How can I accumulate a binary array containing 0 and 1 into an integer?
vector<int> arr = {1,0,1,0,1,1,1,0,1,0,0};
int num = accumulate(
arr.begin(), arr.end(),
[](int &a, int &...
- 351
1
vote
2
answers
652
views
Fix "lambda has no capture-default" [duplicate]
I'm using lambdas for the first time and having a problem which I can't figure out.
I'm getting multiple errors:
<source>: In lambda function:
<source>:7:19: error: 'x' is not captured
...
- 37
6
votes
2
answers
123
views
Is it legal to call the pointer which points to a lambda that is out of scope?
Is it legal to call the pointer which points to a lambda that does not exist anymore?
Here is the demo code snippet.
#include <iostream>
typedef int (*Func)(int a);
int main()
{
Func fun;
{
...
- 3,354
0
votes
0
answers
41
views
Should I use lambda functions where a free function could have been used? [duplicate]
Imagine I have a .cpp file, which inside has some helper code. I can put that code inside some anonymous namespace. Are there disadvantages to use a lambda function for this? Example:
namespace {
...
- 3,332
1
vote
2
answers
221
views
Where is a lambda stored?
This is follow-up question to Does a C++ lambda have a limited life?.
In my previous question, trying to use a lambda after it had gone out of scope caused a crash. While it shouldn't have been ...
- 5,829
43
votes
4
answers
7k
views
Lambda passed by reference runs when invoked in the constructor, but not when later stored in a data member
The following C++ code prints 11.1 then crashes. The lambda function seems to be called correctly inside the constructor, but then later, that same function no longer works! Why is this happening? ...
- 5,829
3
votes
2
answers
76
views
Why copy constructor is called in capture list of lambda
#include <iostream>
#include <vector>
#include <functional>
using namespace std;
struct B {
B() {
std::cout<<"B"<<std::endl;
}
B(B&...
- 1,024
0
votes
1
answer
90
views
why should I use function instead of named lambdas in C++
Recently I've struggled a lot with function deduction and of course lambdas prove to be more flexible here, but doing so I've came to a question, why should I use function instead of named lambdas?
e....
- 119
3
votes
1
answer
84
views
Returning with a Local Variable in a Function Template
In the example below the function template is returning with a local variable and it works as expected even though the return value is not a reference. Is there a lifetime extension scenario in here? &...
- 107
0
votes
1
answer
127
views
Can function templates slow compilation
I have a class with a function template.
class Foo {
public:
void Foo_fn1();
template <typename Closure>
void Foo_util (Closure&& closure) {
Foo_fn1();
std::forward<...
- 8,509
2
votes
1
answer
169
views
Function composition with functor - Performance overhead
As we know, in C++ 11, can't deduce the return type of function returning lambda with auto or decltype(auto). So can't use code like below.
template <typename F, typename G>
constexpr decltype(...
- 533
1
vote
2
answers
91
views
function::target(): How does the template type work for lambdas?
I want to store a lambda expression in a function object, then retrieve its underlying function pointer. For reasons I do not understand, function::target() is a templated function that returns ...
- 622
27
votes
2
answers
2k
views
Can Different Lambdas Decay to the Same Function Pointer?
Can two different lambdas (that have no capture, and the same args and body) decay to the same function pointer?
I have this code:
#include <cassert>
#include <type_traits>
int main() {
...
- 9,587