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When I am using map.contains() in my C++ code using Visual Studio Code I get the following message:

class "std::map<int, int, std::less, std::allocator<std::pair<const int, int>>>" has no member "contains"

Thankfully, my code compiles when I run g++ -std=c++20 test.cc -o test, but VSCode keeps telling me there's a problem, which is quite irritating. This is my code:

#include <map>
using namespace std;

map<int, int> m;

bool contains_key(int idx) { return m.contains(idx); }

Has anyone had the same issue and knows how to fix it?

Wiktor
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    [map::contains](https://en.cppreference.com/w/cpp/container/map/contains) was only added in C++20, so it won't compile unless you configure vscode to use that language revision. – cigien Oct 05 '21 at 19:29
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    look in `cpp_properties.json` – rioV8 Oct 05 '21 at 19:32
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    [this question](https://stackoverflow.com/questions/49397233/how-to-enable-c17-support-in-vscode-c-extension) on enabling C++17 support should also guide you to enabling C++20. – Drew Dormann Oct 05 '21 at 20:00

1 Answers1

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std::map::contains() was introduced in C++20, which is why it works when you configure your compile to use C++20.

For earlier C++ versions, you will have to use std::map::find() or std::map::count() instead:

bool contains_key(int idx) { return m.find(idx) != m.end(); }

bool contains_key(int idx) { return m.count(idx) > 0; }
Remy Lebeau
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