title: ERROR: no match for 'operator<<" in 'std::cout
body: <p>I realize this error is usually due to some syntax or type issues but I am not sure how to solve this problem. I think it may do with the type of findRt.</p>
  
  <pre><code>vector&lt;triangle&gt; findRightTriangles(unsigned long l, unsigned long h) {
  
  &lt;triangle&gt; retval; // storage for return value.
  
  triangle t;    
  double what;
  
  for(t.s1 = 3; t.s1 &lt;= h; t.s1++) {
      for(t.s2 = t.s1; t.s2 &lt;= h; t.s2++) {
          what = sqrt((t.s1*t.s1) + (t.s2*t.s2));
          t.s3 = static_cast&lt;unsigned int&gt;(what);
          if(((t.s1*t.s1)+(t.s2*t.s2)) != (t.s3*t.s3) 
              || t.s1+t.s2+t.s3 &lt; l 
                  || t.s1+t.s2+t.s3 &gt; h) {
              continue;
          }
          else if(t.s1+t.s2+t.s3 &lt;= h 
              &amp;&amp; t.s1+t.s2+t.s3 &gt;= l 
                  &amp;&amp; t.s1+t.s2 &gt; t.s3 
                      &amp;&amp; ((t.s1*t.s1)+(t.s2*t.s2)) == (t.s3*t.s3)) {
              retval.push_back(t);
          }
      }
  }
  return retval;
  }
  
  int main(){
  
  unsigned long min, max;
  
  cin &gt;&gt; min &gt;&gt; max;
  
      //Here is the problem:
  cout &lt;&lt; findRightTriangles(min, max) &lt;&lt; endl;
  
  return 0;
  }
  </code></pre>
  
  <p>How to output the vector using cout?</p>