a=: i.3 4 5 6
(0 0 0 0;1 1 1 1;2 2 2 2){a
0 157 314
(<0 1 2 3)|:a
0 157 314
(<@i.@#@$ |: ]) a
0 157 314
trace=: [: +/ <@i.@#@$ |: ]
trace a
471
On Fri, Sep 4, 2020 at 7:37 PM pietdion <[email protected]> wrote:
> The trace of matrix (2 dimensional array) is implemented with
>
> tr=: +/@:((<0 1)&|:)
>
> (BTW: The "(<0 1)&|:" always mystifies me.)
>
> Can someone point me to an efficient and terse verb that generalises the
> trace to arbitrary dimensions?
> A verb that works on 1 and higher than 2 dimensional arrays.
>
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