Re: Why Return[] does not work?
- To: mathgroup at smc.vnet.net
- Subject: [mg109502] Re: Why Return[] does not work?
- From: image_doctor <eep1mp at googlemail.com>
- Date: Sat, 1 May 2010 06:51:25 -0400 (EDT)
- References: <hr6ihp$2f8$1@smc.vnet.net>
> 2) is there better way to implement intersection check?
You could try this relatively elegant solution ....
IntersectQ[a_, a_] := True
IntersectQ[a_, b_] := False
With the following timing results.
n=100000000;
r1 = RandomInteger[{1,5},{n}];
r2 = RandomInteger[{1,5},{n}];
r3=r1;
Timing[IntersectQ[r1,r1]]
Timing[IntersectQ[r1,r2]]
Timing[IntersectQ[r1,r3]]
Out[55]= {0.,True}
Out[56]= {0.,False}
Out[57]= {0.,True}