Re: functional programming excercise from Mastering Mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg55270] Re: functional programming excercise from Mastering Mathematica*From*: dh <dh at metrohm.ch>*Date*: Fri, 18 Mar 2005 05:33:47 -0500 (EST)*References*: <d1bflp$lja$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hello Torsten, Note that ComposeList takes a function with 1 argument however FoldList a function with 2 arguments. To mimic FoldList using ComposeList, we must first reduce the two argument function to a one argument function by fixing the second argument. This can be done by: Function /@ Thread[fun,{a,b,c}] Therefore, we may define: foldList[fun_,x_,par_List]:=Module[{funs}, funs= Function /@ Thread[fun[#, par]]; ComposeList[funs,x] ] To make it short and cryptic, we can write a one liner: foldList[fun_,x_,par_]:=ComposeList[Function /@ Thread[fun[#, par]], x] Daniel Torsten Coym wrote: > I'm quite new to Mathematica and its functional programming capabilities > so I did some reading in John Gray's "Mastering Mathematica". There is > an excercise in chapter 6 as follows > > Write your own function composeList that works just like the built-in > operation with the same name, using FoldList. Conversely, write your own > function foldList that works just like the built-in operation with the > same name, using ComposeList. > > Unfortunately, there is no solution given at the end of the book (or I > didn't find it). I could figure out a way to do the first task: > > composeList[funlist_List, var_] := FoldList[(#2[#1]) &, var, funlist] > > but I can't manage the second task... > > I know it's rather academic, but ... any help is welcome! > > Torsten >