Re: Programming: List Structure Manipulation

• To: mathgroup at christensen.cybernetics.net
• Subject: [mg971] Re: [mg872] Programming: List Structure Manipulation
• From: Allan Hayes <hay%haystack at christensen.cybernetics.net>
• Date: Thu, 4 May 1995 05:14:26 -0400

```Xah Y Lee <xyl10060 at fhda.edu> [mg872] Programming: List Structure
Manipulation

Writes

> Can anyone show me better ways to write the following function?
>
> fun[listA_, styleList_]:=
>   Table[
>      Append[
>          Flatten@{ First@RotateLeft[styleList,t-1] },  listA[[t]]
>      ],
>      {t, Length@listA}
>  ]
>
> Examples:
>
> fun[Range[0,5],  {a}]         returns
>
>{{a, 0}, {a, 1}, {a, 2}, {a, 3}, {a, 4}, {a, 5}}
>
>
>--
>fun[Range[0,5],  {a,b,c}]         returns
>
>{{a, 0}, {b, 1}, {c, 2}, {a, 3}, {b, 4}, {c, 5}}
>
>--
>fun[Range[0,10],  {{a1, a2}, b}]         returns
>
>{{a1, a2, 0}, {b, 1}, {a1, a2, 2}, {b, 3}, {a1, a2, 4}, {b, 5},
{a1, >a2, 6}, {b, 7}, {a1, a2, 8}, {b, 9}, {a1, a2, 10}}
>
>--
>fun[Range[0,10],  {{a1, a2}, {{b}}, {c1,c2} }]         returns
>
>
>{{a1, a2, 0}, {b, 1}, {c1, c2, 2}, {a1, a2, 3}, {b, 4}, {c1, c2, 5},
>   {a1, a2, 6}, {b, 7}, {c1, c2, 8}, {a1, a2, 9}, {b, 10}}

In[1]:=
fun2[listA_, styleList_]:=
With[{ls = Length[styleList], lA = Length[listA]},
Flatten/@
Transpose[
{
Take[Join@@
Table[styleList, {Ceiling[(lA)/ls]}],
lA
],
listA
}
]
]

Append is a very inefficient operation.
Better to set up a list structure and then reshape it as a whole

Allan Hayes
hay at haystack.demon.co.uk

```

• Prev by Date: Re: Challenge!
• Next by Date: Re: Challenge!
• Previous by thread: Re: Programming: List Structure Manipulation
• Next by thread: Options and FilterOptions