Hello all,
I'm new to clojure, but not lisp.
I'm looking for a functional way to index/number only some items
of a list.
For example, I know I can do this (indexed is from the contrib
seq_utils library):
(using a short example to
keep it readable)
(indexed "Now is")
-> ([0 \N] [1 \o] [2 \w] [3 \space] [4 \i] [5 \s])
What I would like to do is only index those elements that satisfy
some predicate, such as:
(indexed-pred vowel? "Now is")
-> ([\N] [0 \o] [\w] [\space] [1 \i] [\s])
I want the counter to only increment when the predicate is true,
so just filtering out the index on a fully indexed list isn't what I
need, it will leave holes in the numbering.
I'd be OK with the return result being: ([nil \N] [0 \o] [nil \w]
[nil \space] [1 \i] [nil \s])
since a simple map could strip the nils out.
I can't help feeling that the solution is just on the edge of my
peripheral vision, but I can't see it.
Thanks,
-Doug
P.S. I want to use this to number the instructions in a road rally,
where the sequence of instructions are interspersed with other notes
and items. Numbering the vowels in a string is a nice simplification.
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