Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2000
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2000

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Appending an element to a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23910] Re: Appending an element to a list
  • From: Hartmut Wolf <hwolf at debis.com>
  • Date: Fri, 16 Jun 2000 00:56:51 -0400 (EDT)
  • Organization: debis Systemhaus
  • References: <8i9nta$27l@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Felix Farkas schrieb:
> 
>  i do have a problem, which is probably very easy,  but i couldn't find
> a reasonable way to solve it. I would appreciate very much any hint.
> 
> I have a list of lists. My purpose is to append a new elements to this
> list. These elements are generated by some function. Sometimes the
> output of the function is an empty list meaning no element. In this
> situation Append includes the new element in the list. i would like to
> avoid this behaviour.
> 
> ex:
> 
> In[1]:=           d={}
> Out[1]=         {}
> 
> In[2]:=           Append[{{2,2},{3,3}},d]
> Out[2]:=        {{2,2},{3,3},{}}
> 

Perhaps this might be useful:

In[1]:= appendnoemptylistTo[expr_, {}] := expr
In[2]:= appendnoemptylistTo[expr_, elem_] := AppendTo[expr, elem]
In[3]:= b = d = e = {};

In[7]:= collector = {};
In[8]:= 
Scan[appendnoemptylistTo[Unevaluated[collector], #] &, {a, b, c, d, e, f}]

In[9]:= collector
Out[9]= {a, c, f}

Kind regards,
	Hartmut Wolf



  • Prev by Date: Re: Integrate returns 0
  • Next by Date: Manipulating List Elements In Programs
  • Previous by thread: RE: Appending an element to a list
  • Next by thread: Re: Appending an element to a list