Re: generalized foldlist problem
- To: mathgroup at smc.vnet.net
- Subject: [mg69091] Re: generalized foldlist problem
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Wed, 30 Aug 2006 06:32:22 -0400 (EDT)
- Organization: The Open University, Milton Keynes, UK
- References: <ed0rja$sll$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Arkadiusz Majka wrote:
> DearAll,
>
> Please, help!
>
> I have two list
>
> list1={a,b,c,d,e}
> list2={3,2,5,1,6}
>
> and I want to apply a modified version of FoldList to list1 in the
> following way: list2 indicates that element a appears only 3 times (if
> space enough) beginning from the beginning of the list , element b
> appears 2 times, c - 5 times , etc.
>
> So the output should be
>
> GeneralizedFoldList[list1,list2]={a,a+b,a+b+c,c+d,c+e}
>
> Thanks for any hints,
>
> arek
>
Hi Arek,
The following code function should be a good start:
GeneralizedFoldList[list1_List, list2_List] /; Length[list1] ==
Length[list2] :=
Module[
{lst = Transpose[{list1, list2}],
len = Length[list1]},
Plus @@ MapIndexed[PadRight[Table[#1[[1]],
{#1[[2]]}], len, 0, #2[[1]] - 1] & , lst]
]
list1 = {a, b, c, d, e};
list2 = {3, 2, 5, 1, 6};
GeneralizedFoldList[list1, list2]
--> {a, a + b, a + b + c, c + d, c + e}
Regards,
Jean-Marc