From: dvandeun@... (Dirk van Deun)
Date: 2006-02-20T22:53:31+09:00
Subject: dirty ranges

I'm a new Ruby user (currently at page 68 of Programming Ruby !) and
having found something weird, I wonder if either a) "you have already
found a bug, report it" or b) "yeah, yeah, we all know that this is
a bit weird, but it is not a problem in practice".

It seems that you can do destructive operations on the minimum element
of a range, but not on the maximum element (well, you can, but it
does not have any effect):

irb(main):001:0> rng="a".."z"
=> "a".."z"
irb(main):002:0> rng.min[0]="b"
=> "b"
irb(main):003:0> rng.max[0]="y"
=> "y"
irb(main):004:0> rng
=> "b".."z"

This just doesn't seem right.

Actually this was the second thing I found that doesn't seem right.
The first was that the first element is shared when you convert
a range into an array (again, the last one is different):

irb(main):005:0> arr=rng.to_a
=> ["b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
irb(main):006:0> rng.min[0]="c"
=> "c"
irb(main):007:0> rng.max[0]="x"
=> "x"
irb(main):008:0> arr
=> ["c", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]

This is really dirty, but at least this was to be expected from the
specifications ("All you need to be able to make ranges is 'succ' and
'<=>'" -- there is no talk of a deep copy as a requirement.)

Comments ?

Dirk van Deun
-- 
Ceterum censeo Redmond delendum