MathGroup Archive 2006

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: List difference using patterns and substitutions.


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


  • Prev by Date: Re: Arithmetic Puzzle (so simple it's hard)
  • Next by Date: Re: linux font rotation in graphics & (strange) black graphics borders
  • Previous by thread: List difference using patterns and substitutions.
  • Next by thread: Re: List difference using patterns and substitutions.