Question

I found this on another stack question:

//http://stackoverflow.com/questions/3418231/c-replace-part-of-a-string-with-another-string
//
void replaceAll(std::string& str, const std::string& from, const std::string& to) {
    size_t start_pos = 0;
    while((start_pos = str.find(from, start_pos)) != std::string::npos) {
        size_t end_pos = start_pos + from.length();
        str.replace(start_pos, end_pos, to);
        start_pos += to.length(); // In case 'to' contains 'from', like replacing 'x' with 'yx'
    }
}

and my method:

string convert_FANN_array_to_binary(string fann_array)
{
    string result = fann_array;
    cout << result << "\n";
    replaceAll(result, "-1 ", "0");
    cout << result << "\n";
    replaceAll(result, "1 ", "1");
    return result;
}

which, for this input:

cout << convert_FANN_array_to_binary("1 1 -1 -1 1 1 ");

now, the output should be “110011”

here is the output of the method:

1 1 -1 -1 1 1  // original
1 1 0 1  // replacing -1's with 0's
11 1  // result, as it was returned from convert_FANN_array_to_binary()

I’ve been looking at the replaceAll code, and, I’m really not sure why it is replacing consecutive -1’s with one 0, and then not returning any 0’s (and some 1’s) in the final result. =\

Answer 1

The bug is in str.replace(start_pos, end_pos, to);

From the std::string doc at http://www.cplusplus.com/reference/string/string/replace/

string& replace ( size_t pos1, size_t n1,   const string& str );

You are using an end-position, while the function expects a length.

So change to:

while((start_pos = str.find(from, start_pos)) != std::string::npos) {
         str.replace(start_pos, from.length(), to);
         start_pos += to.length(); // ...
}

Note: untested.