CODEWITHSUNDEEP
c++eigenstl-algorithm
SlowCar
SlowCar

Reputation: 3

Get an error using std::upper_bound on an Eigen library vector

I am trying to use std::upper_bound with a vector defined by the Eigen libraries. I get some errors on visual studio 2017

#include <stdafx.h>
#include <stdio.h>
#include <Eigen/Dense>
#include <algorithm>  

using namespace Eigen;
using namespace std;

int main(int argc, char* argv[])
{
    VectorXd myVector= VectorXd::LinSpaced(20, -1.5, 6.4);

    double trashold= strtod(argv[1], NULL);

    double firstGreaterValue= std::upper_bound(myVector(0), 
    myVector(myVector.size()-1),trashold);
}

I expect the program to return the position of the first element that is greater than my input (that in this case is 1.1).

I get these errors on compiling

Severity    Code    Description Project File    Line    Suppression State
Error   C2794   'difference_type': is not a member of any direct or indirect base class of 'std::iterator_traits<_FwdIt>'   errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2347    
Error   C2938   '_Iter_diff_t<double>' : Failed to specialize alias template    errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2347    
Error   C2672   'std::distance': no matching overloaded function found  errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2347    
Error   C2893   Failed to specialize function template 'iterator_traits<_Iter>::difference_type std::distance(_InIt,_InIt)' errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2347    
Error   C2794   'difference_type': is not a member of any direct or indirect base class of 'std::iterator_traits<_FwdIt>'   errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2351    
Error   C2938   '_Iter_diff_t<double>' : Failed to specialize alias template    errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2351    
Error   C2672   'std::advance': no matching overloaded function found   errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2353    
Error   C2893   Failed to specialize function template 'void std::advance(_InIt &,_Diff)'   errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2353    
Error   C2100   illegal indirection errorExample    C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.10.25017\include\algorithm   2355

Upvotes: 0

Views: 641

Answers (1)

xskxzr
xskxzr

Reputation: 13040

Until Version 3.4, Eigen::VectorXd is not compatible with STL algorithms since it does not provide iterators to access its elements.

Since Version 3.4, Eigen's dense matrices and arrays provide STL compatible iterators, then you can use begin()/end() method to get the iterator:

auto firstGreaterValueIter = std::upper_bound(myVector.begin(), myVector.end(), trashold);

Also don't forget std::upper_bound returns an iterator, so you must dereference to get the value:

if (firstGreaterValueIter != myVector.end()) {
    double firstGreaterValue = *firstGreaterValueIter;
    // ...
}

Upvotes: 2

Related Questions