Re: functional routine for {a, b, c, ...} -> {a - b, b - c, c - ...}
- To: mathgroup at smc.vnet.net
- Subject: [mg24902] Re: functional routine for {a, b, c, ...} -> {a - b, b - c, c - ...}
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Sun, 20 Aug 2000 01:34:52 -0400 (EDT)
- References: <8nli50$9fa@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Maarten, Drop[lst, -1] - Drop[lst, 1] {a - b, b - c, c - d, d - e, e - f, f - g, g - h} -- seems about as fast as ListCorrelate. -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 <Maarten.vanderBurgt at icos.be> wrote in message news:8nli50$9fa at smc.vnet.net... > Hallo, > > element. > I found two ways for doing this: > > lst = {a, b, c, d, e, f, g, h}; > > Table[lst[[i]] - lst[[i + 1]], {i, 1, Length[lst] - 1}] > {a - b, b - c, c - d, d - e, e - f, f - g, g - h} > > ListCorrelate[{1, -1}, lst] > {a - b, b - c, c - d, d - e, e - f, f - g, g - h} > > The first method is rather clumsy and the 2nd one is quite short, but not > really obvious. > Initally I was looking for a functional programming style routine. > Something like: (#[[i]]-#[[i-1]])&/@lst. > Who can tell me how to do this in a functional programming style? > > Thanks > > Maarten van der Burgt > Leuven, Belgium > > >