Databases
StackOverflow2013
Postsdbo
POHow can I further specialize this template idea?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow can I further specialize this template idea?
    primarykey
    data
    text
    <p>I can do this with a template specialization I think, for nestedness of 1,2,3 (most common cases) by respectively nesting 1,2,3 for loops and referring to the types by their typenames in stl...but for arbitrary depth, without use of the preprocessor, is there a way to do this? Maybe with mpl? Or would I need a preprocessor tool as well? Right now I am doing something like this:</p> <pre><code>template&lt;typename T, int&gt; struct MapDump {}; template&lt;typename T &gt; struct MapDump&lt;T,1&gt; { static void dump(const T&amp; map, string file, string header="") { if (!header.empty()) cout &lt;&lt; header &lt;&lt; endl; for (typename T::const_iterator cIt = map.begin(); cIt != map.end(); ++cIt) cout &lt;&lt; cIt-&gt;first &lt;&lt; "," &lt;&lt; cIt-&gt;second &lt;&lt; endl; } }; template&lt;typename T &gt; struct MapDump&lt;T,2&gt; { static void dump(const T&amp; map, string file, string header="") { if (!header.empty()) cout &lt;&lt; header &lt;&lt; endl; for (typename T::const_iterator it1 = map.begin(); it1 != map.end(); ++it1) for (typename T::mapped_type::const_iterator it2 = it1-&gt;second.begin(); it2 != it1-&gt;second.end(); ++it2) cout &lt;&lt; it1-&gt;first &lt;&lt; "," &lt;&lt; it2-&gt;first &lt;&lt; "," &lt;&lt; it2-&gt;second &lt;&lt; endl; } }; </code></pre> <p>which I can call with, for example:</p> <pre><code> map&lt;int, map&lt;int, double&gt; &gt; m; m[1][1] = 1.0; m[1][2] = 1.0; m[2][1] = 2.0; m[2][2] = 2.0; MapDump&lt; map&lt;int, map&lt;int, double&gt; &gt;, 2 &gt;::dump(m, "test.csv"); </code></pre> <p>(I stripped out the fstream stuff and left std::cout to simplify the sample code here) My question is, how can I go about specializing when, say, the last level mapped_type is a container type? For example map > is technically a 2-depth construct and not a one level construct...but my nest of 2 specialization wouldn't compile for that type...any other suggestions on how to, perhaps abstract thsi further (figure out the depth of the construct at compile time as well) are welcome..thanks!</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USildjarn
    1. USPalace Chan
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow can I further specialize this template idea?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow can I further specialize this template idea?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POHow can I further specialize this template idea?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COCan you use c++11 and variadic templates?
      singulars
      1. POHow can I further specialize this template idea?
      1. USjrok
    2. COYou need to recurse down the nested mapped_types until you reach a dead end and build functors along the way. I'll try to get something going.
      singulars
      1. POHow can I further specialize this template idea?
      1. USpmr
    3. CO@pmr Yea I sort of though of a recursive down-traversal but i'd have to sit down and think about it harder, how about the nuisance of something like map<int, vector<double> > or map<int, set< vector<int> > > ?
      singulars
      1. POHow can I further specialize this template idea?
      1. USPalace Chan
 

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