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POHow to make std::map compare to work on multiple data types?
 

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  1. POHow to make std::map compare to work on multiple data types?
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    <p>I've a entire table stored in <code>std::deque&lt;record *&gt;</code> and I need to allow the user to sort the table on any column. The table is presented to the user in a list box format.</p> <p>Each record consists of multiple strings (struct of strings). However, the fields are of different types i.e., time (HH:MM:SS), float, and strings, even though they are all stored as strings.</p> <p>The user is permitted to sort on any of these columns. When the user clicks on the column, I store each record in a multimap so that the table is shown in sorted format to the user.</p> <p>However, since the columns are of different types, how do I write a single compare method, that handles all these efficiently?</p> <p>I thought of the following ways</p> <ol> <li>Use different maps for each type and write one compare function class for each of the maps.</li> <li>Use a single map, with a compare class that handles all three different types. But for each insertion, the comparison class has to decide the type , and insert accordingly. </li> </ol> <p>Is there a better way than these two?</p> <p>Example:</p> <pre><code>struct ltDataCompare { bool operator()( const CString&amp; csData1, const CString&amp; csData2) const { if ( isTimeFormat(csData1) &amp;&amp; isTimeFormat(csData1) ) { // Do time relevant comparision } else if ( isNumberFormat( csTime1 ) &amp;&amp; isNumberFormat(csTime2) ) { double dPrice1 = atof((LPCTSTR)csTime1); double dPrice2 = atof((LPCTSTR)csTime2); return ( dPrice1 &lt; dPrice2); } return ( csTime1 &lt; csTime2 ); } }; std::multimap&lt;CString,list_record_t*,ltDataCompare&gt; _mapAllRecords; // Used only for sorting </code></pre>
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    1. USuser373215
    1. USuser373215
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    1. COWhat are you comparing? Does it makes sense to compare a float to a string, for example? Edit: sorry, I see what you mean. You want to sort on one or more fields in the record. Well, you can do that with a field enum which you pass into your sort function (or lambda), then use the appropriate value in the comparison function depending on the enum value.
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      1. POHow to make std::map compare to work on multiple data types?
      1. USRobinson
    2. COCould you please shown an example Robinson?
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      1. POHow to make std::map compare to work on multiple data types?
      1. USuser373215
    3. CORobinson, all fields are stored as strings. I need to determine the type of the field and do appropriate sorting/comparison.
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      1. POHow to make std::map compare to work on multiple data types?
      1. USuser373215
 

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