Intersection[...,SameTest] ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg33054] Intersection[...,SameTest] ?*From*: Konstantin L Kouptsov <klk206 at is5.nyu.edu>*Date*: Wed, 27 Feb 2002 00:48:19 -0500 (EST)*Organization*: New York University*Sender*: owner-wri-mathgroup at wolfram.com

Intersection[..., SameTest->test] seem to do just that. However: 1. It is not clear from the manual (book or help browser), what this command is supposed to return. 2. It simply does not work: In[83]:= a={1,2,3,4}; b={2,4,7,8}; Intersection[a,b,SameTest->(#1==2*#2&)] Out[83]= {1} or more sophisticated: In[85]:= a={1,2,3,4}; b={2,4,7,8}; Intersection[a,b,SameTest-> ((Print[#1,"=?=",#2]||True) &==2*#2 &&(Print[True]||True)&) ] 2 =?= 1 True 3 =?= 1 4 =?= 3 2 =?= 1 True 4 =?= 3 4 =?= 4 Out[85]= {1} which does not seem to enumerate all pairs. What idea stands behind this function? what is supposed to do? (well, for my task I sure could run double For[] cycle, but I am curious about Intersection[])