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Re: Cheaper to prepend or append an item to a sequence

Subject: Re: Cheaper to prepend or append an item to a sequence?
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Tue, 22 Feb 2011 14:32:33 +0000
Re:  Cheaper to prepend or append an item to a sequence
On 22/02/2011 13:58, Dimitre Novatchev wrote:
The accepted term in most functional programming languages is "a list".

A list is a functional data structure (immutable). Appending to a list
causes the whole list to be copied and is O(N). Prepending a list is
making just the "next pointer" of an item point to the list -- an O(1)
operation.


Even with a forward-chained list, you can implement append without copying if you choose, at least for the first append operation to a given list (which 9 times out of 10 will be the only append operation).


Michael Kay
Saxonica

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