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*To*: srfi-113@xxxxxxxxxxxxxxxxx*Subject*: Re: checking set intersection*From*: Kevin Wortman <kwortman@xxxxxxxxx>*Date*: Fri, 20 Dec 2013 20:45:06 -0800*Delivered-to*: srfi-113@xxxxxxxxxxxxxxxxx*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type:content-transfer-encoding; bh=kkp2QeeNk7YOPLX6ORXYnbKb63k6VtNAt5mLoD06LHg=; b=LY+yD+0SERFWyBdzVHWlgH9jwlSPKNKwA/ZzWpc37zphe5Tq0IuWWNJgRN1I/He3u5 n3UQCcDW4MFnbuA2He6WhKgAcDfRGVoX3Vd2emz+85Fbr+mVDd/5BgLvkV/qX+6NeOY4 BVj3DMwjJfFmlHyv9efKKa1HJ3d5fTIMAvsVpoDJzIm6iHRywkMdk6ZvzWxzAUNpsvaR K0vCkbglhTEeofxEcsdFBXHF2DRVj7simsr3ZkZC6UPFq9BA2b+XOp0yXgeGSbuFyXzG SaPmlnqGN29VrmT9v49COzR157a5OHIrYy5p/+OSdoYLgAKuvQy29ICr1GnsRP25mobo 3SYQ==*In-reply-to*: <CAMMPzYOPJEbsSe6vdQZa1=5Lu6oKoPtSxzdWV_KaN-HpikyPwA@mail.gmail.com>*References*: <CAMMPzYOPJEbsSe6vdQZa1=5Lu6oKoPtSxzdWV_KaN-HpikyPwA@mail.gmail.com>*User-agent*: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0

On 12/19/2013 04:25 PM, Alex Shinn wrote: > I've had uses for testing whether two sets > intersect without needing the actual > intersection, so I think the following would > be useful: > > (define (set-intersects? a b) > (positive? (set-size (set-intersection a b)))) > > though it could be implemented much > more efficiently. > > I was originally going to write this as > > (not (set-empty? ...)) > > but realized there was no such predicate. > We might want to include that as well. This is a good point and I second the request for set-intersects? and set-empty?. Both should be easy enough to implement. We already have predicates for set equality, subsets, proper subsets, and are now discussing intersection. We might as well add a set-disjoint? predicate too so that all the fundamental set relationships are represented. Kevin Wortman

**Follow-Ups**:**Re: checking set intersection***From:*John Cowan

**References**:**checking set intersection***From:*Alex Shinn

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