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POUnexpected results using istringstream for string to double conversion in C++
 

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  1. POUnexpected results using istringstream for string to double conversion in C++
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    <p>I'm currently trying to take a string ("0.1") and convert it to a double using C++ in Xcode on 10.6 with gcc4.2.</p> <p>I'm using a function I pinched from <a href="https://stackoverflow.com/questions/392981/how-can-i-convert-string-to-double-in-c">another question</a>, but when I try to use the function, my input according to gdb is (string)"0.1", but my output is (double)2.1220023981051542e-314.</p> <p>Here is my snippet copied straight out the code:</p> <pre><code>double strToDouble(std::string const &amp;numberString) { istringstream inStream(numberString); double doubleValue; inStream &gt;&gt; doubleValue; if(!(inStream &amp;&amp; (inStream &gt;&gt; std::ws).eof())) { return 0.0; } return doubleValue; }; </code></pre> <p>I'm using C++ rather than Obj-C, as it will probably have to be compiled on a *nix or windows machine eventually.</p> <p>I'm naturally a PHP programmer, but have some number crunching I need to speed up, so I'm doing it in a compiled language. It's been a long time since University dealing with a lower level language =P. So, if anyone has an ideas, it would be greatly appreciated...</p> <p>Drew J. Sonne.</p> <p>Full code:</p> <pre><code>#include &lt;iostream&gt; #include &lt;vector&gt; #include &lt;string&gt; #include &lt;sstream&gt; using namespace std; /* * @var delimiters the string to define a break by * @var str the string to break * @var tokens where to store the broken string parts. */ void explode(const string&amp; delimiters, const string&amp; str, vector&lt;string&gt;&amp; tokens) { // Skip delimiters at beginning. string::size_type lastPos = str.find_first_not_of(delimiters, 0); // Find first "non-delimiter". string::size_type pos = str.find_first_of(delimiters, lastPos); while (string::npos != pos || string::npos != lastPos) { // Found a token, add it to the vector. tokens.push_back(str.substr(lastPos, pos - lastPos)); // Skip delimiters. Note the "not_of" lastPos = str.find_first_not_of(delimiters, pos); // Find next "non-delimiter" pos = str.find_first_of(delimiters, lastPos); } }; /* * @var numberString double to be converted as a string. */ double strToDouble(std::string const &amp;numberString) { istringstream inStream(numberString); double doubleValue; inStream &gt;&gt; doubleValue; if(!(inStream &amp;&amp; (inStream &gt;&gt; std::ws).eof())) { return 0.0; } return doubleValue; }; class Cluster { private: vector&lt;double&gt; latStore; vector&lt;double&gt; lngStore; public: Cluster(int,string,string); }; /* * @var latString a comma seperated list of doubles for the latitudes. * @var lngString a comma separated list of doubles for the longitudes. */ Cluster::Cluster(int newLocationLength, string latString, string lngString) { // mark our vectors vector&lt;string&gt; latStoreString; vector&lt;string&gt; lngStoreString; // Explode our input strings. explode(",", latString, latStoreString); explode(",", lngString, lngStoreString); for( int i = 0; i &lt; latStoreString.size(); i++) { // Grab the latitude and store it. string tempLat = latStoreString[i]; double latDouble = strToDouble(tempLat); latStore.push_back( strToDouble(tempLat) ); // Grab the longitude and store it. string tempLng = lngStoreString[i]; lngStore.push_back( strToDouble(tempLng) ); } } int main (int argc, char * const argv[]) { Cluster *rect = new Cluster("0.1,0.4","0.1,0.4"); return 0; } </code></pre>
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    1. COOdd. When I run this code targeting 10.6 Debug, I get the 0.0 returned from the if check. If I compile 10.6 Release, everything works fine. Targeting 10.5 works for both Debug and Release. Don't know what the problem is.
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    2. COAwesome. Thanks Anthony. It works here when I change it to 10.5. Never even crossed my mind. 10.5 is is then. If you put it as an answer, I can mark it right, and you can get more BrowniePoints™. =P
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    3. COGlad it got you running. The cause of the problem seems to be as indicated by cdespinosa's answer. I'd mark that one as the accepted answer.
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