Re: newbie list question

*To*: mathgroup at smc.vnet.net*Subject*: [mg114996] Re: newbie list question*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Tue, 28 Dec 2010 06:47:48 -0500 (EST)

On 12/26/10 at 4:02 AM, gareth.edwards at cubicmotion.com (Gareth Edwards) wrote: >Liking Mathematica a lot, but struggling with the early part of the >learning curve, i.e. don't know what I don't know... >What would be the neatest syntax for finding the first location of >elements from one list in another? For example: >listA = { 4,5,8,2,6,4 } listB = { 8,4,2 } >I would like a function to return {3,1,4} in this case (the first >location in A of each element in B) Neatest will always be a matter of opinion. Here is one way In[4]:= listA = {4, 5, 8, 2, 6, 4}; listB = {8, 4, 2}; Position[listA, #][[1, 1]] & /@ listB Out[6]= {3,1,4} Here I am using the /@ (shorthand for Map) to map a pure function, the Position[listA,#][[1,1]]& part, to each element of listB