Simple MapReduce Example

>(mapreduce identity +
            '(((a 3) (b 2) (c 1))
              ((b 7) (d 3) (c 5))) t)
Mapping: ((A 3) (B 2) (C 1))
   Emitted: (A 3)
   Emitted: (B 2)
   Emitted: (C 1)
Mapping: ((B 7) (D 3) (C 5))
   Emitted: (B 7)
   Emitted: (D 3)
   Emitted: (C 5)
Reducing: D (3)    = 3
Reducing: C (5 1)  = 6
Reducing: B (7 2)  = 9
Reducing: A (3)    = 3

((D 3) (C 6) (B 9) (A 3))