Re: list equation

*To*: mathgroup at smc.vnet.net*Subject*: [mg121974] Re: list equation*From*: Chris Arthur <chris.arthur1 at gmail.com>*Date*: Fri, 7 Oct 2011 04:51:02 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201110060824.EAA22708@smc.vnet.net>

Table[{i,j},{i,1,i},{j,1,100}] On Thu, Oct 6, 2011 at 3:24 AM, dimitris <dimmechan at yahoo.com> wrote: > Hello to all. > > Let > > lst = Tuples[Range[100], 2]; > > In the previous list appear elements such us {x,y} and {y,x}. (e.g. > {3,4} and {4,3}). > I want to create a new list with {y,x} dropped (that is, in the new > list appears only {3,4} > and not {4,3}). > > I use > > lstnew = Union[lst, SameTest -> (#1 == Reverse[#2] &)] > > However it is needed almost 150 sec for this procedure ($Version->5.2 > for Windows) > I know that my laptop is too old but I guess there is a more efficient > way to > create lstnew. > > Any ideas? > > Thanks a lot > > Dimitris >

**References**:**list equation***From:*dimitris <dimmechan@yahoo.com>