Re: Simple List question. HELP.

*To*: mathgroup at smc.vnet.net*Subject*: [mg39445] Re: Simple List question. HELP.*From*: Bill Rowe <listuser at earthlink.net>*Date*: Sat, 15 Feb 2003 01:43:21 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

On 2/14/03 at 3:24 AM, MarkCWestwood at compuserve.com (Mark Westwood) wrote: >Far better to use Append all the time. Note too that, like many a >functional programming language Append[list, value] does NOT change >list ! It returns the list made by appending value to list. What you >probably want is: >list = Append[list, value] >that is, make an explicit assignment which causes the old version of >list to be replaced by its new version, with value added. If you >continue to Append in this way you'll probably notice a piling up of >curly brackets. No, Append will not cause "a piling up of curly brackets". Try for example In[1]:= lst={}; lst=Nest[Append[#,{Random[],Random[]}]&,lst,5]; Depth[lst] Out[3]= 3 But it is also true building up lists in this manner is not the fastest way to do things. A faster way to build up a list would be lst = {lst,next element} which will cause "a piling up of curly brackets" For example, In[4]:= lst={}; Timing[lst=Nest[Append[#,{Random[]}]&,lst,10000];] Out[5]= {25.02 Second,Null} In[6]:= lst={}; Timing[lst=Flatten[Nest[{#,Random[]}&,lst,10000]];] Out[7]= {0.08 Second,Null}