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 Double +:  0 0 0 Not-Or

 +: y is twice y . For example: ``` +: 3 0 _2 6 0 _4 ``` x +: y is the negation of x or y . For example, 0 +: 0 is 1 .

Since the square of the sum of two arguments equals the sum of their squares and twice their product, the following functions are equivalent:
```   f=: + * +
g=: *:@[ + +:@* + *:@]
```
For example:
```   x=: 7 6 3 [ y=: 6 5 3
x (f ; g ; (f=g) ; (f-:g)) y
+----------+----------+-----+-+
|169 121 36|169 121 36|1 1 1|1|
+----------+----------+-----+-+
```
Since the domain of not-or is limited to zero and one, its entire behaviour can be seen in the following function tables:
```   d=: 0 1                    NB. Domain of nor
d +:/ d                    NB. Table of nor
1 0
0 0

d +./ d                    NB. Table of or
0 1
1 1

-. d +./ d                 NB. Negation of table of or
1 0
0 0

(+:&.-./~d) ; (*:/~d)      NB. Nand and nor are duals under not
+---+---+
|1 1|1 1|
|1 0|1 0|
+---+---+

```

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