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  1. Core Server
  2. SERVER-6165

use of an integer valued double with a $mod expression can produce an incorrect result

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      Observed behavior: If one of the arguments to $mod is a double, the left argument is cast to an int (not a long long) before the modulus is calculated. This can result in a loss of information in the left operand before the modulus is calculated.
      Expected behavior: Casting to an int does not occur in this case because it can alter the $mod result due to data loss.

      c = db.c;
c.drop();

c.save( {} );

// The correct mod is calculated.
assert.eq( 1, c.aggregate( { $project:{ z:{ $mod:[ NumberLong('4294967296'), NumberLong( 3 ) ] } } } ).re\
sult[ 0 ].z );

// An incorrect mod is calculated due to a lossy integer conversion in ExpressionMod::evaluate.
assert.eq( 1, c.aggregate( { $project:{ z:{ $mod:[ NumberLong('4294967296'), 3.0 ] } } } ).result[ 0 ].z \
);

            Assignee:
            matt.dannenberg Matt Dannenberg
            Reporter:
            aaron Aaron Staple
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              Created:
              Updated:
              Resolved: