how would you represent a null tree in a forest?

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1

say my trees are nested lists of integers of varying rank. how would you represent the null tree?


if i choose 0 for null, to test for the existence of a null tree in the forest:

q)(0~')(1 2;0)

01b


then |/ to reduce


q)0 in(1 2;0) /doesn’t work because in is rank sensitive

0b


is there a better value for the null tree?

2

Why not define a function to recursively find a null tree:

q)ntree:{1b in (,/) $[0>(@)x;0 in x;nt each x]}

q)ntree (1 3;5)

0b

q)ntree ((9;(4 5));0)

1b

q)nt (1 2;4;(2;(4;(0 5 6));4))

1b

Tiago

3

On my previous post ntree and nt were the same function:

Here is the correct definition:

ntree:{1b in (,/) $[0>(@)x;0 in x;ntree each x]}

Or in an arguably more readable q:

ntree:{1b in raze $[0>type x;0 in x;ntree each x]}