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POTemplate Class – Symbols not found
 

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  1. POTemplate Class – Symbols not found
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    <p>I've seen a few <a href="https://stackoverflow.com/questions/1682844/templates-template-function-not-playing-well-with-classs-template-member-functi">related</a> <a href="https://stackoverflow.com/questions/999358/undefined-symbols-linker-error-with-simple-template-class"> posts</a>, but I can't really make sense of what I need to do to fix a program I'm making for my entry-level C++ class.</p> <p>My errors are:</p> <pre><code>Build Final Project of project Final Project with configuration Debug Ld "build/Debug/Final Project" normal x86_64 cd "/Users/nick/Dropbox/|Syncs/Xcode/Final Project" setenv MACOSX_DEPLOYMENT_TARGET 10.6 /Developer/usr/bin/g++-4.2 -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.6.sdk "- L/Users/nick/Dropbox/|Syncs/Xcode/Final Project/build/Debug" "-F/Users/nick/Dropbox/|Syncs/Xcode/Final Project/build/Debug" -filelist "/Users/nick/Dropbox/|Syncs/Xcode/Final Project/build/Final Project.build/Debug/Final Project.build/Objects-normal/x86_64/Final Project.LinkFileList" -mmacosx-version-min=10.6 -o "/Users/nick/Dropbox/|Syncs/Xcode/Final Project/build/Debug/Final Project" Undefined symbols: "Vector&lt;double&gt;::Vector()", referenced from: _main in main.o "Vector&lt;double&gt;::length()", referenced from: _main in main.o "Vector&lt;double&gt;::Vector(double const&amp;, double const&amp;, double const&amp;)", referenced from: _main in main.o _main in main.o "Vector&lt;double&gt;::getx() const", referenced from: _main in main.o _main in main.o "Vector&lt;double&gt;::gety() const", referenced from: _main in main.o _main in main.o ld: symbol(s) not found collect2: ld returned 1 exit status </code></pre> <p>Here's what I've got:</p> <pre><code>//main.cpp #include &lt;iostream&gt; #include "Vector.h" int main () { Vector&lt;double&gt; a(1, 2, 3); Vector&lt;double&gt; b(2, 4, 4); Vector&lt;double&gt; c; std::cout &lt;&lt; "Length: " &lt;&lt; b.length() &lt;&lt; std::endl; std::cout &lt;&lt; b.getx() &lt;&lt; " ," &lt;&lt; b.gety() &lt;&lt; std::endl; std::cout &lt;&lt; c.getx() &lt;&lt; " , " &lt;&lt; c.gety() &lt;&lt; std::endl; return 0; } </code></pre> <p>and</p> <pre><code>//Vector.h template &lt;class T&gt; class Vector { T x, y, z; public: //constructors Vector(); Vector(const T&amp; x, const T&amp; y, const T&amp; z); Vector(const Vector&amp; u); //accessors T getx() const; T gety() const; T getz() const; //mutators void setx(const T&amp; x); void sety(const T&amp; y); void setz(const T&amp; z); //operations void operator-(); Vector plus(const Vector&amp; v); Vector minus(const Vector&amp; v); Vector cross(const Vector&amp; v); T dot(const Vector&amp; v); void times(const T&amp; s); T length(); }; </code></pre> <p>and the Vector.cpp (though I've trimmed some code that's somewhat duplicative – accessors &amp; mutators for y and z, for instance)</p> <pre><code>//Vector.cpp #include "Vector.h" #include &lt;iostream&gt; #include &lt;math.h&gt; template class Vector&lt;int&gt;; template class Vector&lt;double&gt;; //default constructor template &lt;class T&gt; Vector&lt;T&gt;::Vector(): x(0), y(0), z(0) {} //constructor template &lt;class T&gt; Vector&lt;T&gt;::Vector(const T&amp; x, const T&amp; y, const T&amp; z) { setx(x); sety(y); setz(z); } //copy constructor template &lt;class T&gt; Vector&lt;T&gt;::Vector(const Vector&amp; u) { x = u.getx(); y = u.gety(); z = u.getz(); } //x accessor template &lt;class T&gt; T Vector&lt;T&gt;::getx() const { return x; } //y accessor //z accessor //x mutator template &lt;class T&gt; void Vector&lt;T&gt;::setx(const T&amp; x) { Vector::x = x; } //y mutator //z mutator //negated Vector template &lt;class T&gt; void Vector&lt;T&gt;::operator-() { setx(-this-&gt;getx()); sety(-this-&gt;gety()); setz(-this-&gt;getz()); } //sum template &lt;class T&gt; Vector&lt;T&gt; Vector&lt;T&gt;::plus(const Vector&amp; v) { Vector ret((getx() + v.getx()), (gety() + v.gety()), (getz() + v.getz())); return ret; } //difference template &lt;class T&gt; Vector&lt;T&gt; Vector&lt;T&gt;::minus(const Vector&amp; v) { Vector ret((getx() - v.getx()), (gety() - v.gety()), (getz() - v.getz())); return ret; } //cross product template &lt;class T&gt; Vector&lt;T&gt; Vector&lt;T&gt;::cross(const Vector&amp; v) { Vector ret; ret.setx(gety()*v.getz() - getz()*v.gety()); ret.sety(getz()*v.getx() - getx()*v.getz()); ret.setz(getx()*v.gety() - gety()*v.getx()); return ret; } //dot product template &lt;class T&gt; T Vector&lt;T&gt;::dot(const Vector&amp; v) { return (getx()*v.getx() + gety()*v.gety() + getz()*v.getz()); } //scalar times Vector template &lt;class T&gt; void Vector&lt;T&gt;::times(const T&amp; s) { setx(getx()*s); sety(gety()*s); setz(getz()*s); } //length of Vector template &lt;class T&gt; T Vector&lt;T&gt;::length() { return sqrt((this-&gt;dot(*this))); } </code></pre> <p>So, what the hell's going on? Is it because I have a separate header &amp; .cpp file for Vector? How do I get my main function to recognize functions of my Vector class?</p>
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    1. USCommunity
    1. USNick Sweet
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      1. POTemplate Class – Symbols not found
      1. USPardeep
      1. VTFavorite
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      1. POTemplate Class – Symbols not found
      1. USAlan S
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      1. VTUpMod
    1. COOne source of information is the [C++ FAQ](http://www.parashift.com/c++-faq-lite/templates.html#faq-35.12), a good [book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) likes *"Templates - The Complete Guide"* would also help.
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      1. USGeorg Fritzsche
 

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