error: ‘infinity’ does not name a type

Question

I have a program which contain many cpp files,I try to create a makefile but when I run it I got some errors related to this function:

void replace_infinites(cv::Mat_<int>& matrix) {
const unsigned int rows = matrix.rows,columns = matrix.cols;
//  assert( rows > 0 && columns > 0 );
if(rows==0 || columns==0)
    return;
double max = matrix(0, 0);
const auto infinity = std::numeric_limits<int>::infinity();

// Find the greatest value in the matrix that isn't infinity.
for ( unsigned int row = 0 ; row < rows ; row++ ) {
    for ( unsigned int col = 0 ; col < columns ; col++ ) {
        if ( matrix(row, col) != infinity ) {
            if ( max == infinity ) {
                max = matrix(row, col);
            } else {
                max = std::max<int>(max, matrix(row, col));
            }
        }
    }
}

// a value higher than the maximum value present in the matrix.
if ( max == infinity ) {
    // This case only occurs when all values are infinite.
    max = 0;
} else {
    max++;
}

for ( unsigned int row = 0 ; row < rows ; row++ ) {
    for ( unsigned int col = 0 ; col < columns ; col++ ) {
        if ( matrix(row, col) == infinity ) {
            matrix(row, col) = max;
        }
    }
}

} I tried to include :

#include <limits> 

using namespace std;

But when I compile my program I get these errors:

munkres.cpp: In function ‘void replace_infinites(cv::Mat_<int>&)’:
munkres.cpp:44:16: error: ‘infinity’ does not name a type
munkres.cpp:49:38: error: ‘infinity’ was not declared in this scope
munkres.cpp:60:17: error: ‘infinity’ was not declared in this scope
munkres.cpp:69:38: error: ‘infinity’ was not declared in this scope

I make a lot of research on the net but I didn't get any solution to fix my problem.

Answer 1

It seems likely that you are not compiling with C++11 or higher, since your compiler is complaining about the following line:

const auto infinity = std::numeric_limits<int>::infinity();

Assuming you have indeed included #include <limits> , there is nothing wrong with that line except the use of auto . Without C++11, the compiler doesn't know what auto is. Compile with C++11 or higher, or change auto to int .

Unrelated, and this was pointed out in the comments, but using numeric_limits<int>::infinity is an awful, awful way of checking things. It doesn't make any sense to make an int comparison in regards to infinity. Prefer to usenumeric_limits<int>::max instead (or whatever else suits your purposes).