Re: Partitioning lists

*To*: mathgroup at smc.vnet.net*Subject*: [mg20509] Re: Partitioning lists*From*: Hans Staugaard <hans.staugaard at get2net.dk>*Date*: Wed, 27 Oct 1999 02:05:05 -0400*Organization*: get2net Internet Kunde*References*: <7v3dfq$63d@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

DIAMOND Mark wrote: > > I would like a function f to split a list as follows > > a={1,2,3,4,5,6} > f[a] = > { > {{1},{2,3,4,5,6}}, > {{1,2},{3,4,5,6}}, > {{1,2,3},{4,5,6}}, > {{1,2,3,4},{5,6}}, > {{1,2,3,4,5},{6}} > } > > I can do this as > > Table[{Take[a, i], Drop[a, i]}, {i, 1, Length[a] - 1}] > > but it *looks* as though it is very inefficient. Is it? > It also looks as though there should be a way of using Partition simply to > chop a list between positions i and i+1, but > I cannot see how to do it. Any suggestions? > > mark diamond > no spam email: markd at psy dot uwa dot edu dot au Here's a suggestion In[1]:= t = Range[6] Out[1]= {1, 2, 3, 4, 5, 6} In[2]:= ReplaceList[t, {a__, b__} -> {{a}, {b}}] Out[2]= {{{1}, {2, 3, 4, 5, 6}}, {{1, 2}, {3, 4, 5, 6}}, {{1, 2, 3}, {4, 5, 6}}, {{1, 2, 3, 4}, {5, 6}}, {{1, 2, 3, 4, 5}, {6}}} I imagine it is not very efficient for large list. Hans