Re: List difference using patterns and substitutions.

*To*: mathgroup at smc.vnet.net*Subject*: [mg71325] Re: [mg71306] List difference using patterns and substitutions.*From*: Sseziwa Mukasa <mukasa at jeol.com>*Date*: Wed, 15 Nov 2006 06:43:19 -0500 (EST)*References*: <200611141006.FAA06710@smc.vnet.net>

On Nov 14, 2006, at 5:06 AM, Nacho wrote: > 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? This isn't the kind of problem I'd attempt with pattern matching. Subtract[#2,#1]&@@@Partition[list,2,1] gives you the result you want. Regards, Ssezi

**References**:**List difference using patterns and substitutions.***From:*"Nacho" <ncc1701zzz@gmail.com>