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 Oblique m/.  u/. _ _ _ Key

 u/.y applies u to each of the oblique lines of a table y . For example: ``` i.3 4 0 1 2 3 4 5 6 7 8 9 10 11

The application of a function to diagonals of a table is commonly useful, as in correlation, in convolution, and in products of polynomial coefficients (or, equivalently, products of numbers in a fixed base). For example:
```   t=: p */ q [ p=: 1 2 1 [ q=: 1 3 3 1

t ; (+//.t) ; 1 1 &(+//.@(*/)) ^: (i.6) 1
+-------+-------------+-------------+
|1 3 3 1|1 5 10 10 5 1|1 0  0  0 0 0|
|2 6 6 2|             |1 1  0  0 0 0|
|1 3 3 1|             |1 2  1  0 0 0|
|       |             |1 3  3  1 0 0|
|       |             |1 4  6  4 1 0|
|       |             |1 5 10 10 5 1|
+-------+-------------+-------------+

((10#.p)*10#.q), 10 #. +//. p */ q
161051 161051
```

Unlike polynomial coefficients, the diagonal sums of a multiplication table of digits should be “normalized” if any equal or exceed the radix.

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