Question

I have a text file that reads:

this is an email file with [e-mail] and some other text for the test
[e-mail]
[e-mail]

And then I have a substr (s, e - s), where s is the start of the line and e is the end that will give me this:

terminate called after throwing an instance of 'std::out_of_range'
what():  basic_str`entering::substr
Aborted

This only occurs for the bottom two lines, and the first will print [e-mail]

The problem I know is what is happening is when s is at the beginning of the line and there are no characters before it (i.e. “[e-mail]” or “[e-mail]”), this error occurs. What could be added to prevent this from occuring?

while (getline(fin, lines))
{
for (int i = 0; i < lines.length(); i++)
{
if (lines[i] == '@')
{
int s;

if (i == 0 || i == 1) break;
for (s = i - 1; s < lines.length() ; s--)
{
if(validChar(lines[s]) == false )
 {
 s = s + 1;
 break;
 }
} //for 

 int e; 
 bool hasDot = false;  

 for (e = i + 1; e < lines.length(); e++)
 {
 if (e == lines.length()) break;
 if(validChar(lines[e]) == false )
 {
 break;
 } // if in for

 if(lines[e] == '.') hasDot = true;
 } // for 

anEmail = lines.substr (s,  e - s);
if (s < i && e > i && hasDot == true)
cout << anEmail << endl; 

Answer 1

Obviously, one of your paramaters are out of range becase of the out_of_range exception that was thrown. I would run some test to make sure that the values s and e are what you would expect them to be.