From: no.top.post@...
Date: 2011-05-17T04:40:23+09:00
Subject: Re (2): Linux utility with reverse index facility?

In article <r5g7a8-3a5.ln1@206-248-139-163.dsl.teksavvy.com>, "Chris F.A. Johnson" <cfajohnson@gmail.com> wrote: 

> On 2011-05-16, no.top.post@gmail.com wrote:
> > awk &stuff can "give me the the Nth element",
> > but, without writing your own search-loop,
> > what can "give me the index of the 'element'
> > which is <elementValue>" ?
> >
> > I think it's called 'reverse indexing' ?
> 
>    Do you want 'grep -n'?
> 
>    If not, please be more specific.

awk & grep are not typically used on arrays of single chars,
but that's the simplest, to ilustrate the concept.
Given the 6char array: [abcdef]
<elementValue> means the value of the element.
The first element has value "a".
"the  index of the 'element' which is "e" is
<the 5th element>; which index is  4 or 5 depending
on whether you count from 0 or 1 respectively.

So what did I mean by "writing your own search-loop"?

AFAIK ruby has <assocoation <memory-structures>>.
That mean ruby has structures which operate like association
memories; so you can ask "what's the index of the element
which has value "dog", in the 'structure' of strings.

== Chris Glur.