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Real / Imaginary +.  0 0 0 GCD (Or)

+.y yields a two-element list of the real and imaginary parts of its argument. For example, +.3j5 is 3 5, and +.3 is 3 0 .
 
  x+.y is the greatest common divisor of x and y . If the arguments are boolean (0 or 1), the functions +. and *. are equivalent to logical or and and. The function -. similarly restricted is not.
 

   ]y=: i+2*j. i=: i.4
0 1j2 2j4 3j6

   +. y
0 0
1 2
2 4
3 6
The greatest common divisor divides both of its arguments x and y to produce results that have no common factor, that is, the GCD of the quotients is 1. Moreover, these quotients represent the fraction x%y in lowest form. For example:
   x=: 24 [ y=: 60
   x;y;(x +. y);((x , y) % (x +. y))
+--+--+--+---+
|24|60|12|2 5|
+--+--+--+---+

   lff=: , % +.               Gives lowest form of fraction
   x;y;(x lff y);(%/x lff y);(%/x,y);(+./x lff y)
+--+--+---+---+---+-+
|24|60|2 5|0.4|0.4|1|
+--+--+---+---+---+-+
Since the functions =| and =<. (tests for non-negative and for integer) produce boolean results, the phrase (=|)+.(=<.) is a test for non-negative or integer:
   (test=: (=|) +. (=<.)) _2 _2.4 3 3.5
1 0 1 1
The duality of or and and may be shown as follows:
   d (+./ ; *.&.-./ ; *./ ; +.&.-./) d=: 0 1
+---+---+---+---+
|0 1|0 1|0 0|0 0|
|1 1|1 1|0 1|0 1|
+---+---+---+---+


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