Hello, all!

I have a list of characters and a boolean list of 1s and 0s.  I
thought that I could use the boolean list as a "mask" to choose
characters by using "and" (*.).  But the definition in NuVoc basically
states that it can only be used with numbers (no literals).

Here's an example of the kind of thing I'd like to be able to do:

chars=. 'ABCDEFGHIJKLM'
mask=. 0 1 0 0 1 0 1 0 0 0 0 0 0   [boolean values]

mask2=. 0 1 0 0 4 0 6 0 0 0 0 0 0   [positions of boolean values]

I thought that I could do something like  chars *. mask to get the
result BEG.  That doesn't work nor does converting the mask to
position numbers (mask2) work.  So how *can* I mask the characters?
I'd be interested in knowing both the "pure" boolean kind of approach
(1s and 0s only) as well as a positional approach that I can use with
amending.

My ultimate goal is actually to amend the masked characters to be a
different character(s).  I hope I've given enough information.  (The
example, of course, is completely "fake", but I hope it gives the idea
of what I'm trying to do.)

Thanks for any help!

Harvey
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