Re: List Position

*To*: mathgroup at smc.vnet.net*Subject*: [mg15797] Re: [mg15740] List Position*From*: Andrzej Kozlowski <andrzej at tuins.ac.jp>*Date*: Sun, 7 Feb 1999 02:04:13 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

On Fri, Feb 5, 1999, Harry flynn <harry.f at ukonline.co.uk> wrote: >Can anyone tell me how I find the position in a list of the first value >less than or equal to zero. >For example, how can I get Mathematica to tell me that in the list >{{1},{1},{2},{8},{-3}} >that the first value of interest to me is position 5. Thanks in advance. >Harry. > Here is one way to do it. In[4]:= findfirstnegative[l_]:=Position[l,Scan[If[#<0,Return[#]]&,l,Infinity]] Now if you define In[5]:= l={{1},{1},{2},{8},{-3}} you get In[6]:= findfirstnegative[l] Out[6]= {{5, 1}} This actually works with any expression, not just a list: In[7]:= findfirstnegative[1/x] Out[7]= {{2}} Andrzej Kozlowski Toyama International University JAPAN http://sigma.tuins.ac.jp/ http://eri2.tuins.ac.jp/