Indexes of elements inside a vector.

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1

Hi, 
a:vector of 1s and 0s. (1 0 1 1 1 0 1 1 1 1 1 0 0 0 1 0 … )

I want to do something similar to (0=a)/?(?a),(APL syntax). This returns the indices of elements inside a, that are equal to 0.

APL ? -> is equal to the ‘til’ inside q.

APL ? -> is equal to ‘count’ inside q.

the / (over) function inside q seems to be the best choice, however, I’m lost for an answer. 

How could I implement this inside q? (I’m assuming the ‘over’ function behaves the same as in APL’s /, which seems to be the case, looking at the reference.)

Thanks, 

Kumar

2

I think you need:
where a=0

3

q)a:1 0 1 1 1 0 1 1 1 1 1 0 0 0 1 0
q)where a
0 2 3 4 6 7 8 9 10 14

or if you’re exploring k as well:
q)<br> &a
0 2 3 4 6 7 8 9 10 14