Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>You have to be careful when you use <strong>friend</strong> and <strong>template</strong></p> <pre><code>#include&lt;iostream&gt; #include&lt;map&gt; template &lt;class T&gt; class MyHash{ public: // ... use your T template here template &lt;class U&gt; friend ostream&amp; operator&lt;&lt;(ostream&amp; out, const MyHash&lt;U&gt; &amp;rhs); }; // ... template &lt;class U&gt; ostream&amp; operator&lt;&lt;(ostream&amp; out, const MyHash&lt;U&gt; &amp;rhs){ return out &lt;&lt; "test"; } </code></pre> <p>you need to use a different <strong>template U</strong> because <strong>operator&lt;&lt;</strong> is a <strong>friend</strong> method (external), if we use <strong>T</strong> instead of <strong>U</strong>, we will have : <strong>ambiguous definition in template </strong>.</p> <p>Change <strong>hash</strong> by <strong>MyHash</strong> to avoid ambiguities.</p> <p><strong>Edit :</strong> </p> <p>The error that you get <a href="https://github.com/everett1992/couple-solver/tree/master/test_dir" rel="nofollow">here</a> is :</p> <blockquote> <p>error C2676: '&lt;' binaire : 'std::string' ne définit pas cet opérateur ou une conversion vers un type acceptable pour l'opérateur prédéfini</p> </blockquote> <p>because you forgot to include <code>&lt;string&gt;</code> in <strong>"hash.h"</strong>. That header defines the <strong>&lt; operator</strong>. </p> <p>And also try moving the definition of <strong>operator[]</strong> and <strong>operator&lt;&lt;</strong> directly into <strong>"hash.h"</strong> Both the declaration and definition of templates must be included. This is because in some compilers template functions cannot be compiled and linked independently, since they are generated on request for the specific types they are instantiated with.</p> <p>Change the <strong>#include "hash.cpp"</strong> to <strong>#include "hash.h"</strong></p>
    singulars
    1. This table or related slice is empty.
    1. POHow do you declare the friend of a generic class outside of the class decleration?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USOuadie
    1. USOuadie
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POHow do you declare the friend of a generic class outside of the class decleration?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI have a follow up question: when I use your solution, and I place the function definition in a different file than the class decleration I need to include the .cpp file with the definition, and not the .h file when i try and use that class. What am I doing wrong?
      singulars
      1. PO
      1. USeverett1992
    2. CO[here](https://github.com/everett1992/couple-solver/tree/master/test_dir) is an example of what I'm talking about. If I were to compile this as it is everything is ok, but if i change the include hash.cpp to hash.h in test.cpp, and compile with g++ test.cpp hash.cpp then it doesnt compile
      singulars
      1. PO
      1. USeverett1992
    3. CObriefly include <string> in "hash.h", or read the Edit part in my answer for more details.
      singulars
      1. PO
      1. USOuadie
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload