Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Sylvia Else Newsgroups: comp.misc Subject: Thoughts in combinatorial logic Date: Mon, 1 Apr 2019 16:11:04 +1100 Lines: 18 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: individual.net Ub5j7az6xIQ3RaU3MDO7+wfFyQrPNtOsH0vrkxb7EgWGytxOVm Cancel-Lock: sha1:Dv/8DCl8x7LZd9qV/CtzRBPbZN0= X-Mozilla-News-Host: news://news.individual.net:119 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 Content-Language: en-GB Xref: csiph.com comp.misc:17715 As part of a personal project I'm working on, I needed a combinatorial logic way of obtaining the lowest set bit from a collection of bits. That is, taking n inputs in some order, and by using only and/or/not gates, produce n outputs of which only one is set, being that which corresponds to the lowest order set input bit It's not especially difficult. But suppose the requirement is not the lowest set bit, just any of the set bits. Clearly, the solution to the first requirement is also a solution to the second requirement, but is the second requirement amenable to a simpler (as in, using fewer gates) solution. My intuition is that it's not, but I haven't been able to prove it. Sylvia.