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Integers | i. 1 _ _ | Index Of

The shape of`i.y` is`|y` ,`` and its atoms are the first`*/|y` non-negative integers. A negative element in`y` causes reversal of the atoms along the corresponding axis. For example:

       i. 5
    0 1 2 3 4

       i. 2 _5
    4 3 2 1 0
    9 8 7 6 5

If`rix` is the rank of an item of`x`,`` then the shape of the result of `x i. y` is`(-rix)}.$y` .`` Each atom of the result is either`#x` or the index of the first occurrence among the items of`x` of the corresponding`rix-`cell of`y` .
The comparison in`x i. y` is tolerant, and fit can be used to specify the tolerance, as in`i. !. t` .

       (i.4);(i._4);(i.2 3 4);(i.2 _3 4);(i.'')
    +-------+-------+-----------+-----------+-+
    |0 1 2 3|3 2 1 0| 0  1  2  3| 8  9 10 11|0|
    |       |       | 4  5  6  7| 4  5  6  7| |
    |       |       | 8  9 10 11| 0  1  2  3| |
    |       |       |           |           | |
    |       |       |12 13 14 15|20 21 22 23| |
    |       |       |16 17 18 19|16 17 18 19| |
    |       |       |20 21 22 23|12 13 14 15| |
    +-------+-------+-----------+-----------+-+

       A=: 'abcdefghijklmnopqrstuvwxyz'
       (A i. 'Now');(A i. 'now');(A {~ A i. 'now')
    +--------+--------+---+
    |26 14 22|13 14 22|now|
    +--------+--------+---+

       m=: 5 4 $ 12{. A
       m;(m i. 'efgh');(1{m);(4{m)
    +----+-+----+----+
    |abcd|1|efgh|efgh|
    |efgh| |    |    |
    |ijkl| |    |    |
    |abcd| |    |    |
    |efgh| |    |    |
    +----+-+----+----+

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