dcsimg
CodeGuru Home VC++ / MFC / C++ .NET / C# Visual Basic VB Forums Developer.com
Results 1 to 11 of 11

Thread: [RESOLVED] An error in my code - binary digit matrix implementation by using 2D vector

  1. #1
    Join Date
    Mar 2018
    Posts
    37

    [RESOLVED] An error in my code - binary digit matrix implementation by using 2D vector

    Hello

    [/HTML]
    Last edited by Kmilano; April 23rd, 2018 at 09:51 AM.

  2. #2
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
    Jan 2003
    Location
    Hanover Germany
    Posts
    19,229

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    Quote Originally Posted by Kmilano View Post
    ...
    when I use vectors which I commented in the following code without void function everything is okay and if I want to merge them into one vector like following with void function I will have an error in this line:

    HTML Code:
    for (const auto& row : generate_mtx(nbits))
    1. Please, post the exact error text.
    2. Please, use CODE tags, not the HTML ones!
    Victor Nijegorodov

  3. #3
    Join Date
    Mar 2018
    Posts
    37

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    the errors:
    1
    main.cpp||In function ‘int main()’:|
    2
    main.cpp|40|error: invalid initialization of reference of type ‘std::vector<std::vector<int> >&’ from exp<b></b>ression of type ‘size_t {aka long unsigned int}’|
    3
    main.cpp|12|note: in passing argument 1 of ‘void generate_mtx(std::vector<std::vector<int> >&, std::size_t)’|
    4
    main.cpp|42|error: unable to deduce ‘auto&&’ from ‘row’|
    5
    ||=== Build failed: 2 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|
    Last edited by Kmilano; April 23rd, 2018 at 09:52 AM.

  4. #4
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
    Jan 2003
    Location
    Hanover Germany
    Posts
    19,229

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    Quote Originally Posted by Kmilano View Post
    the errors:
    1
    main.cpp||In function ‘int main()’:|
    2
    main.cpp|40|error: invalid initialization of reference of type ‘std::vector<std::vector<int> >&’ from exp<b></b>ression of type ‘size_t {aka long unsigned int}’|
    ...
    Code:
    ...
    		for (const auto& row : generate_mtx(nbits))
    		{
    			for (int v : row) std::cout << v << ' ';
    			std::cout << '\n';
    		}
    ...
    Your code refers to the function generate_mtx(nbits), however the only function with this name is declared as void, so it cannot return anything...
    Sure, it is not what you expected!
    Victor Nijegorodov

  5. #5
    Join Date
    Mar 2018
    Posts
    37

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    in fact,
    Last edited by Kmilano; April 23rd, 2018 at 09:51 AM.

  6. #6
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
    Jan 2003
    Location
    Hanover Germany
    Posts
    19,229

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    Quote Originally Posted by Kmilano View Post
    in fact, first my code was like the following code and it works correctly, but because I must use void function to match base class with a derived class, so I changes that line to void function,
    now, what's a solution to solve this error?
    You could implement the overloaded method in your derived class that would either return your created vector or you would pass this vector as a parameter by reference into your method.
    Variant 1 (pseudo code):
    Code:
    typedef std::vector< std::vector<int> > myMatrix;
    
    myMatrix generate_mtx(std::size_t nbits)
    {
    	nbits %= std::numeric_limits<unsigned long long>::digits;
    
    	myMatrix result(nbits);
    
    	// note: col with all zeroes is skipped (start with number = 0 to include it)
    	for (unsigned long long number = 1; number < ubound(nbits); ++number)
    	{
    		auto n = number;
    		for (auto& vec : result)
    		{
    			vec.push_back(n % 2);
    			n /= 2;
    		}
    	}
    	std::reverse(std::begin(result), std::end(result));
    
    	return result;
    }
    Variant 2 (pseudo code):
    Code:
    typedef std::vector< std::vector<int> > myMatrix;
    
    myMatrix generatedMatrix;
    void generate_mtx(std::size_t nbits, myMatrix& generatedMatrix)
    {
    	nbits %= std::numeric_limits<unsigned long long>::digits;
    
    	// note: col with all zeroes is skipped (start with number = 0 to include it)
    	for (unsigned long long number = 1; number < ubound(nbits); ++number)
    	{
    		auto n = number;
    		for (auto& vec : generatedMatrix)
    		{
    			vec.push_back(n % 2);
    			n /= 2;
    		}
    	}
    	std::reverse(std::begin(generatedMatrix), std::end(generatedMatrix));
    }
    Victor Nijegorodov

  7. #7
    2kaud's Avatar
    2kaud is offline Super Moderator Power Poster
    Join Date
    Dec 2012
    Location
    England
    Posts
    6,416

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    Code:
    for (const auto& row : generate_mtx(nbits))
    When using a range-based for loop, the range expression (the return type of generate_mtx(nbits) in this case) needs to be of a type that supports the begin() and end() iterator functions so that the range can be obtained. vector<> does but void doesn't. If generate_mtx() is required to return a void, then generate_mtx() needs to have a reference parameter as Victor uses in Variant 2 in post #6. In this case the range_for would be something like (not tried)

    Code:
    typedef std::vector< std::vector<int> > myMatrix;
    
    myMatrix generatedMatrix;
    generate_mtx(nbits, generatedMatrix);
    
    for (const auto& row : generatedMatrix)
    {
        for (int v : row)
            std::cout << v << ' ';
    
        std::cout << '\n';
    }
    All advice is offered in good faith only. All my code is tested (unless stated explicitly otherwise) with the latest version of Microsoft Visual Studio (using the supported features of the latest standard) and is offered as examples only - not as production quality. I cannot offer advice regarding any other c/c++ compiler/IDE or incompatibilities with VS. You are ultimately responsible for the effects of your programs and the integrity of the machines they run on. Anything I post, code snippets, advice, etc is licensed as Public Domain https://creativecommons.org/publicdomain/zero/1.0/ and can be used without reference or acknowledgement. Also note that I only provide advice and guidance via the forums - and not via private messages!

    C++17 Compiler: Microsoft VS2017 (15.8.4)

  8. #8
    Join Date
    Mar 2018
    Posts
    37

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    thank you for your response, but I cannot use matrix and I must use the code which exists in my first post, In my last reply I posted my original correct code, but I cannot use it,
    if its possible please give me an alternative way for correcting the first code:
    Last edited by Kmilano; April 23rd, 2018 at 09:52 AM.

  9. #9
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
    Jan 2003
    Location
    Hanover Germany
    Posts
    19,229

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    [QUOTE=Kmilano;2221795]thank you for your response, but I cannot use matrix
    What "matrix" do you mean?
    if it is the one I referred in my post as
    Quote Originally Posted by Victor
    Code:
    typedef std::vector< std::vector<int> > myMatrix;
    then sorry! It is just a typedef! I used it to make code simpler (to write and to understand!)

    Quote Originally Posted by Kmilano View Post
    if its possible please give me an alternative way for correcting the first code:

    Code:
    #include "stdafx.h"
    #include <iostream>
    #include <limits>
    #include <vector>
    #include <algorithm>
    using namespace std;
    
    constexpr unsigned long long ubound(std::size_t nbits)
    {
    	if (nbits < 2) return 2;
    	else return ubound(nbits - 1) * 2;
    }
    
    //std::vector< std::vector<int> > generate_mtx(std::size_t nbits)
    void generate_mtx(std::vector< std::vector<int> >& result, std::size_t nbits)
    {
    	nbits %= std::numeric_limits<unsigned long long>::digits;
    
    	//std::vector< std::vector<int> > result(nbits);
    
    	// note: col with all zeroes is skipped (start with number = 0 to include it)
    	for (unsigned long long number = 1; number < ubound(nbits); ++number)
    	{
    		auto n = number;
    		for (auto& vec : result)
    		{
    			vec.push_back(n % 2);
    			n /= 2;
    		}
    	}
    
    	// to get the rows in the same order as illustrated in the example  
    	std::reverse(std::begin(result), std::end(result));
    
    	//return result;
    }
    
    int main()
    {
    
    	if (size_t nbits = 4)
    	{
    		std::cout << "check matrix (H) is: " << std::endl;
    
    		for (const auto& row : generate_mtx(nbits))
    		{
    			for (int v : row) std::cout << v << ' ';
    			std::cout << '\n';
    		}
    
    
    	}
    	int pause;
    	std::cin >> pause;
    	//return 0;
    }
    I did it in my previous post.

    Alternatively you could define your "matrix" (std::vector< std::vector<int> >) as a global object but in C++ it is not recommended.
    Victor Nijegorodov

  10. #10
    2kaud's Avatar
    2kaud is offline Super Moderator Power Poster
    Join Date
    Dec 2012
    Location
    England
    Posts
    6,416

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    I think this is what you are after. It produces the required output.

    Code:
    #include <iostream>
    #include <limits>
    #include <vector>
    #include <algorithm>
    using namespace std;
    
    constexpr unsigned long long ubound(std::size_t nbits)
    {
    	if (nbits < 2) return 2;
    	else return ubound(nbits - 1) * 2;
    }
    
    void generate_mtx(std::vector< std::vector<int> >& result, std::size_t nbits)
    {
    	nbits %= std::numeric_limits<unsigned long long>::digits;
    	result.resize(nbits);
    
    	// note: col with all zeroes is skipped (start with number = 0 to include it)
    	for (unsigned long long number = 1; number < ubound(nbits); ++number)
    	{
    		auto n = number;
    		for (auto& vec : result)
    		{
    			vec.push_back(n % 2);
    			n /= 2;
    		}
    	}
    
    	// to get the rows in the same order as illustrated in the example
    	std::reverse(std::begin(result), std::end(result));
    }
    
    int main()
    {
    	if (size_t nbits = 4)
    	{
    		std::vector< std::vector<int> > results;
    
    		std::cout << "check matrix (H) is: " << std::endl;
    		generate_mtx(results, nbits);
    
    		for (const auto& row : results)
    		{
    			for (int v : row) std::cout << v << ' ';
    			std::cout << '\n';
    		}
    	}
    
    	std::cin.get();
    }
    Code:
    check matrix (H) is:
    0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
    0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
    0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
    1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
    Last edited by 2kaud; March 25th, 2018 at 12:25 PM.
    All advice is offered in good faith only. All my code is tested (unless stated explicitly otherwise) with the latest version of Microsoft Visual Studio (using the supported features of the latest standard) and is offered as examples only - not as production quality. I cannot offer advice regarding any other c/c++ compiler/IDE or incompatibilities with VS. You are ultimately responsible for the effects of your programs and the integrity of the machines they run on. Anything I post, code snippets, advice, etc is licensed as Public Domain https://creativecommons.org/publicdomain/zero/1.0/ and can be used without reference or acknowledgement. Also note that I only provide advice and guidance via the forums - and not via private messages!

    C++17 Compiler: Microsoft VS2017 (15.8.4)

  11. #11
    Join Date
    Mar 2018
    Posts
    37

    Re: An error in my code - binary digit matrix implementation by using 2D vector

    yes thank you so much, its my desired code

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


Windows Mobile Development Center


Click Here to Expand Forum to Full Width




On-Demand Webinars (sponsored)