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How to use copy_if() polymorphically?


How to use copy_if() polymorphically?

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How to use copy_if() polymorphically?
Tag : cpp , By : user157138
Date : November 24 2020, 03:41 PM


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are they adding copy_if to c++0x?


Tag : cpp , By : gopal
Date : March 29 2020, 07:55 AM
seems to work fine Since the C++0x is not yet finalized, you can only take a look at the most recent draft.

Difference between using vector polymorphically vs. arrays polymorphically


Tag : cpp , By : ap.
Date : March 29 2020, 07:55 AM
should help you out It's fine to use either an array or vector to hold pointers to polymorphic types.
The problem is if you try to treat an array of objects polymorphically. Array access via a pointer uses the pointer type to determine the size of the array objects, which will go horribly wrong if the pointer type does not match the object type.
Base * stuff = new Derived[10]; // No compile error: pointer conversion is allowed
stuff[2].do_something();        // Still no compile error, but weird runtime errors.

In-place std::copy_if


Tag : cpp , By : toma
Date : March 29 2020, 07:55 AM
To fix the issue you can do copy_if is primarily for copying a range to another range/container I.e. by design, the nature of the algorithm is to copy the elements satisfying some condition to another (non-overlapping) range or to a new container.
remove_if is more appropriate for what you need; it is exactly for filtering out as you expect. However, it only removes the elements by overwriting; the remnants between the old and new ends would be unspecified elements after the function's completion and needs to be manually erased using erase, like so:
std::vector<int> vec { 1, 2, 3, 4 };
vec.erase(std::remove_if(std::begin(vec),
                         std::end(vec),
                         [](int i) { return i <= 2; }),
          std::end(vec));

C++ using copy_if


Tag : cpp , By : Joe
Date : March 29 2020, 07:55 AM
hope this fix your issue I am new to C++ and am trying to use the copy_if function: , You need inserter, plus valid predicate:
std::copy_if(people.begin(), people.end(),
             std::inserter(copyedPeople, copyedPeople.end()),
             [](const auto& person){ return person.getName() == name; });

copy_if with different types


Tag : cpp , By : beng
Date : March 29 2020, 07:55 AM
Hope that helps Using range-v3:
std::vector<Foo> get_valid_foos(const std::vector<FooBar>& foobars) {
    return foobars
        | view::filter(&FooBar::is_valid)
        | view::transform(&FooBar::foo);
}
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