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POMalfunctioning type-casting of string to unsigned int
 

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    <p>I'm having a annoying problem with a C++ function that I wrote and whose purpose is to validate de user input. The function reads the user input, verifies if it's a number and, if so, if it is in the range [min, max].</p> <p>The problem occurs when I invoke the template function with a unsigned type, like <code>size_t</code>, and the input is a negative number. The string stream converts the string to something like 4294967291. I can see that the program is converting the data to a value near de maximum value of the unsigned data type (defined in the numeric_limits header) but my question is why, since the <code>if</code> statement should stop at <code>sstream &gt;&gt; value</code>?</p> <p>My code:</p> <pre><code>template &lt;class T&gt; T getNumberInput(std::string prompt, T min, T max) { std::string input; T value; while (true) { try { std::cout &lt;&lt; prompt; std::cin.clear(); std::getline(std::cin, input); std::stringstream sstream(input); if (input.empty()) { throw EmptyInput&lt;std::string&gt;(input); } else if (sstream &gt;&gt; value &amp;&amp; value &gt;= min &amp;&amp; value &lt;= max) { std::cout &lt;&lt; std::endl; return value; } else { throw InvalidInput&lt;std::string&gt;(input); } } catch (EmptyInput&lt;std::string&gt; &amp; emptyInput) { std::cout &lt;&lt; "O campo não pode ser vazio!\n" &lt;&lt; std::endl; } catch (InvalidInput&lt;std::string&gt; &amp; invalidInput){ std::cout &lt;&lt; "Tipo de dados inválido!\n" &lt;&lt; std::endl; } } } </code></pre> <p>Thank you for your time!</p>
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