From: "Guy N. Hurst" <gnhurst@...>
Date: 2001-04-28T02:43:18+09:00
Subject: [ruby-talk:14340] Re: Immutable Arrays?


Johann Hibschman wrote:
> 
> Hi folks,
> 
> Is there any way to flag an Array as immutable, so I can use it
> as a key in a hash table without worrying about it changing?  This
> is what the "tuple" in python is for, and there I find it useful.
> 
> This comes up, since every now and then I want to simply use [x,y,z]
> points as hash keys, and I would like to have some assurance that
> this will not cause problems.
> 

a = [2,3,4]  # array
a.freeze     # now immutable
a[1] = 0     # TypeError: can't modify frozen array

hsh = { [1,2,3].freeze => "now immutable" }
hsh[[1,2,3]]	#=> "now immutable"


Guy N. Hurst

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