From: dws@cs.wisc.edu (DaviD W. Sanderson)
To: rc@archone.tamu.edu
Subject: Re: how would you do this in rc
Date: Thu, 19 Dec 1991 19:11:12 -0600 [thread overview]
Message-ID: <9112200111.AA20207@skinner.cs.wisc.edu> (raw)
In-Reply-To: <91Dec19.190941est.2742@hawkwind.utcs.toronto.edu>; from "Chris Siebenmann" at Dec 19, 91 6:09 pm
> You have a list l and a string s. What's the most efficient way to not
> merely find out if s exists in l, but to find its index in l if it does?
This probably isn't as efficent as it could be, but it only uses one
external command.
fn index { # str list
str = $1 ans = '' {
shift
while(~ $str $*)
{
shift
ans=$ans^x # count in unary
}
expr $ans : '.*'
#-------
# Use this if you don't have expr
#
# echo `{echo $ans | tr -d '\012' | wc -c}
#-------
}
}
index a (x y z) # 0
index a (a y z) # 1
index a (x a z) # 2
index a (ax y a) # 3
index '' (a '' b) # 2
DaviD W. Sanderson (dws@cs.wisc.edu)
next prev parent reply other threads:[~1991-12-20 1:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
1991-12-20 0:09 Chris Siebenmann
1991-12-20 1:11 ` DaviD W. Sanderson [this message]
1991-12-20 12:21 ` David J. Fiander
1991-12-20 1:27 Tom Culliton x2278
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