Re: List difference using patterns and substitutions.
- To: mathgroup at smc.vnet.net
- Subject: [mg71350] Re: List difference using patterns and substitutions.
- From: Bill Rowe <readnewsciv at sbcglobal.net>
- Date: Wed, 15 Nov 2006 06:44:41 -0500 (EST)
On 11/14/06 at 5:06 AM, ncc1701zzz at gmail.com (Nacho) wrote:
>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?
While there may be a fast way to do this with pattern matching,
there already is a built-in function to do this. Specifically ListConvolve
For example,
In[1]:=
ListConvolve[{1,-1},{a,b,c}]
Out[1]=
{b-a,c-b}
Alternatively
In[2]:=
ListCorrelate[{-1,1},{a,b,c}]
Out[2]=
{b-a,c-b}
--
To reply via email subtract one hundred and four