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List difference using patterns and substitutions.

• To: mathgroup at smc.vnet.net
• Subject: [mg71306] List difference using patterns and substitutions.
• From: "Nacho" <ncc1701zzz at gmail.com>
• Date: Tue, 14 Nov 2006 05:06:25 -0500 (EST)

Hello.

I'm trying to figure how can I build a difference list from another
using only patterns and rule substitutions.

The idea is to get from a list, another, one element shorter, where
each value is the substraction of two consecutive elements in the
original list, that is, from {1,2,3,5,5} get {1,1,2,0}.

I've been thinking about it for a while, and I know several methods
using a more traditional programming style (with For, for example), but
I have no idea if it is possible to make it simple and fast with rule
substitutions.

Any idea? 

Thanks in advance.

• Follow-Ups:
  • Re: List difference using patterns and substitutions.
    • From: gardyloo <gardyloo@mail.wsu.edu>
  • Re: List difference using patterns and substitutions.
    • From: János <janos.lobb@yale.edu>
  • Re: List difference using patterns and substitutions.
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>
  • Re: List difference using patterns and substitutions.
    • From: Sseziwa Mukasa <mukasa@jeol.com>