Re: Intersection problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg125980] Re: Intersection problem*From*: Murta <rodrigomurtax at gmail.com>*Date*: Wed, 11 Apr 2012 18:17:22 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <jm0ju7$adk$1@smc.vnet.net>

On Apr 10, 3:28 am, Cisco Lane <travl... at yahoo.com> wrote: > I need to select out the elements of the first list whose first elements are contained in the second list. For example > > first list: {{a,x},{b,y},{c,z}} > > second list: {b,c,d} > > result: {{b,y},{c,z}} > > Is there a quick way to do this? Intersection, maybe somehow? Hi Lane There are 2 ways to do that: l1 = {{a, x}, {b, y}, {c, z}}; l2 = {b, c, d}; number 1 Select[l1, MemberQ[l2, #[[1]]] &] number 2 Cases[l1, {a_ /; MemberQ[l2, a], _}] best regards Murta