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>