| Halve | -: 0 _ _ | Match | 
| -:y is one half of y .  For example: -: i. 5 0 0.5 1 1.5 2 | x -: y yields 1 if its arguments match: 
in shapes, boxing, and elements; but using tolerant comparison.  
See Equal (=). Matching with a tolerance t can be obtained using the verb -: !. t . | 
   x=: 0 1 2 3 4 5
   ,.&.> (] ; -: ; +:@-: ; (%&2) ; (2: %~ ])) x
+-+---+-+---+---+
|0|  0|0|  0|  0|
|1|0.5|1|0.5|0.5|
|2|  1|2|  1|  1|
|3|1.5|3|1.5|1.5|
|4|  2|4|  2|  2|
|5|2.5|5|2.5|2.5|
+-+---+-+---+---+
      
   x = +: -: x
1 1 1 1 1 1
   x -: +: -: x
1