Re: Taking brackets off lists
- To: mathgroup at christensen.cybernetics.net
- Subject: [mg291] Re: [mg281] Taking brackets off lists
- From: Xah Y Lee <xyl10060 at fhda.edu>
- Date: Mon, 5 Dec 1994 22:29:51 -0800 (PST)
On Sun, 4 Dec 1994, corcoran wrote:
> If I have a list like,
>
> list = {1,1,1,2}
>
> how do I find the part of a expression at the level specified by the list?
> i.e.
>
> I want exp[[1,1,1,2]],
>
> but exp[[list]] doesn't work.
>
> Thanks,
> Stephen
>
mylist = {1,1,1,2};
expr = Table[Random[Integer,{0,10}],{3},{2},{3},{3}];
expr[[Sequence@@mylist]]
or
Part[expr, Sequence@@mylist ]
will give you what you want. Sequence[] is not documented. In general,
f[Sequence[x1,x2,...,xn]] will evaluate to f[x1,x2,...,xn].
Reference: _Programming in Mma_ by Roman Maeder.
Also mentioned in _Mma Quick Ref. v2_ by Nancy Blachman.
Xah
Mountain View, CA
temporary email: xyl10060 at tiptoe.fhda.edu
permament email: 74631.731 at compuserve.com