Thread: why not working?

  1. #1
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    why not working?

    Code:
    #include<vector>
    #include<cmath>
    #include<iostream>
    
    
    
    
    
    
    int main()
    {
        std::vector<int> ints{ 0, 1, 2, 3, 4, 5 };
        auto even = [](int i) { return i % 2 == 0;  };
        auto square = [](int i) { return i * i;  };
    
    
        for (int i : ints | std::views::filter(even) |
            std::views::transform(square)) {
            std::cout << i << ' ';
        }
    }
    It says two errors, but I did the example straight from the book...

  2. #2
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    What exactly are the errors?

  3. #3
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    Quote Originally Posted by jimblumberg View Post
    What exactly are the errors?
    Says:
    Code:
    main.cpp:17:30: error: ‘std::views’ has not been declared   17 |     for (int i : ints | std::views::filter(even) |
          |                              ^~~~~
    main.cpp:18:14: error: ‘std::views’ has not been declared
       18 |         std::views::transform(square)) {       |              ^~~~~

  4. #4
    C++ Witch laserlight's Avatar
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    You need to compile as C++20, or if your compiler does not support C++20, then you need to upgrade compiler.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  5. #5
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    You also need to include <ranges>, then it works with my VS2019

  6. #6
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    I was using C++ 20....

    Quote Originally Posted by laserlight View Post
    You need to compile as C++20, or if your compiler does not support C++20, then you need to upgrade compiler.

  7. #7
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    Can you show your code? Because I used
    Code:
    #include<ranges>
    and it did not work...

    Quote Originally Posted by thmm View Post
    You also need to include <ranges>, then it works with my VS2019

  8. #8
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    It's the same code you posted + the include.
    You also need to set the C++ Language Standard
    why not working?-untitled-1-png
    Attached Images Attached Images why not working?-untitled-1-png 

  9. #9
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    Wow, many thanks. I was using c++ 14, now no longer am. Thank you.

    Quote Originally Posted by thmm View Post
    It's the same code you posted + the include.
    You also need to set the C++ Language Standard
    why not working?-untitled-1-png

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