Re: selecting from lists
- To: mathgroup at smc.vnet.net
- Subject: [mg6134] Re: [mg6120] selecting from lists
- From: Lou Talman <me at talmanl.mscd.edu>
- Date: Sun, 23 Feb 1997 00:10:47 -0500
- Sender: owner-wri-mathgroup at wolfram.com
Murray Eisenberg wrote:
> The problem: given an arbitrary list v and a list b of the same
> length, whose entries are all Boolean (True or False), construct a
> function s[v, b] whose result is a list consisting only of those
> entries of v for which the corresponding entries in b are True. For
> example,
>
> v = {3, 82, 7, -12, 5};
> b = {False, True, True, False};
> s[v, b]
> {82, 7}
How about
s[v_, b_] := Cases[Transpose[{v, b}], {x_, True} -> x]
--Lou Talman