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    <p>Assuming that my psychic abilities for fixing your question's code were right, I'd write it like this: </p> <pre><code>struct mine { int rows int columns std::string array_file } void function(const mine&amp; m) { Matrixint array_name(pt-&gt;rows, std::vector&lt;int&gt;(pt-&gt;columns)); std::ifstream infile(m.array_file.c_str()); for (int a = 0; a &lt; ls-&gt;rows &amp;&amp; infile.good(); ++a) { for (int b = 0; b &lt; ls-&gt;columns &amp;&amp; infile.good(); ++b) { infile &gt;&gt; array_name[a][b] ; } } if(!infile) throw "Uh oh!"; // assume real error handling here } </code></pre> <p>Why have I changed all these things? </p> <ul> <li>A class with all public data isn't a <code>class</code>, but an aggregation of data. I'd use a <code>struct</code> for that, to not to confuse those who later need to maintain my code. (That might include me a few years down the road, which is a strong incentive to be very helpful.)</li> <li>Unless you know exactly what you're doing (which doesn't seem to be the case), you should be using <code>std::string</code> rather than C-style strings. </li> <li><a href="https://stackoverflow.com/questions/2139224/how-to-pass-objects-to-functions-in-c/">Why pass the function parameter by pointer, when you can use a <code>const</code> reference</a>? </li> <li><code>std::ifstream</code> has a constructor with which you can open a file immediately. I rarely ever use (or see used) its <code>open()</code> member function. </li> <li>You need to test whether the file was opened and whether the input operations succeeded. (In this case, I merged the test whether it could be opened with the input operation succeed test, since the for loop is a pre-testing loop.) After the operations, I check whether an error occurred. Alternatively you could break out of the loop with an exception when reading fails. </li> <li>Usually there is no need to close a stream, since its destructor already does this. If you make your variables as local as possible (which is good programming praxis), the file will be closed right away nevertheless. </li> </ul>
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    1. POopening and reading a file whose name is given at runtime
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    1. COThanks for the reply. A few comments upon your comments: - yes, I am new to C++ programming - what was not clear of "among the others"? The class has also private data, but not relevant for the question - the original code is not mine, I'm expanding it, using the same structure imposed by the original programmer - I'm pretty sure of how the data will be formatted, so there is no need of testing whether I am reading beyond the end of the line/file. I agree there could be the need of testing if the file opened, what could cause this? Thanks Federico
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    2. CO@Federico: I simply overlooked the "among the others". Otherwise it's pretty clear. If you want your app to silently fail just because some jerk edited a file he shouldn't have touched (or for any number of other, equally silly reasons), you don't need to check input operations. Otherwise you should. One common but often overlooked causes for failing to open a file is missing access rights, but many others exist.
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