From: Matthew Smillie <M.B.Smillie@...>
Date: 2006-06-11T21:35:45+09:00
Subject: Re: Substrings by Position.

On Jun 11, 2006, at 13:08, Charlie wrote:

>>>    Shouldn't a negative indexing work as well? (Below are just  
>>> examples,
>>> they currently don't work) It will allow strings to be REVERSED  
>>> easily,
>>> and thus doing something new.
>>
>> Negative indexes do work already.  You probably mean negative  
>> lengths.
>
>    Yes, you're right. It just mean lengths with direction.

I don't think that having negative lengths reflect direction is at  
all a natural decision; it's describing the bounds of a substring,  
not describing and implicit iteration through individual characters.   
In other words, if negative lengths worked, I'd fully expect them to  
work like this (y is negative): foo[x, y] == foo[(x+y), y.abs]

e.g.

foo = "0123456789"
foo[4,-1] # => 3
foo[3, 1] # => 3
foo[4,-2] # => 23
foo[2, 2] # => 23

Conflating string reversal into setting the bounds of the substring  
is a mistake, I'd say, particularly since there's already a perfectly  
reasonable String#reverse.

matthew smillie.