Hi -
I'm working with selecting sequential items from a vector given a starting
and an ending point as a pair of integers. If we assume we always get the
pair as (lesser, greater), something like this suffices:
seq=: {. + [: i. [: >: -~/
seq 3 7
3 4 5 6 7
However, if our assumption about the order of our points is violated, we
get nonsense:
seq 7 3
7 8 9
Just for robustness, how could we write a version of "seq" that would
return the sequence in reverse order in this latter case, i.e. give the
proper sequence from seven to three: 7 6 5 4 3 ?
I generalized the "seq" verb to remove the ordering assumption: my idea was
to generate the ascending sequence, then flip it if >/y is true. I tried
this with "agenda" but am not sure how to get it to work on one thing - the
ascending vector - on the basis of comparison of another thing - the pair
of integers.
I did achieve this using the "power" conjunction:
seq=: 3 : '|.^:(>/y)](<./ + [: i. [: >: >./ - <./) y'
seq 3 7
3 4 5 6 7
seq 7 3
7 6 5 4 3
Does anyone have any ideas for a more elegant, preferably tacit, solution?
Thanks,
Devon
--
Devon McCormick, CFA
Quantitative Consultant
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