On 2018-03-28 at 16:50, Abdullah Ramazanoglu wrote: > On Wed, 28 Mar 2018 09:46:53 -0400 The Wanderer said: > >> On 2018-03-28 at 09:39, Laurent Debian wrote: >> >>> Dear all, I have one question Does that aptitude message looks >>> normal to you :" >>> >>> "python-tornado breaks : python-zmq (< 17) but 16.0.2-2+b1 is to >>> be installed" >>> >>> Does I misunderstand or does it looks like aptitude thinks that >>> 16.0... is not less than 17 ? >> >> No, it's saying "because the version of python-zmq which is >> selected for installation is 16.x, we can't install a version of >> python-tornado which says it only works with version 17 and >> above". >> >> Why version 16.x is selected for installation is another question, >> but we don't have enough information to go on in that regard. > > Sorry but I still don't get it. As I understand, aptitude appears to > say that python-zmq with version *less than* 17 is needed?
No. The relationship "Breaks: packagename < X" means that any version of 'packagename' which is less than version X will not work with this package. (Here, "packagename" = "python-zmq" and "X" = "17".) A "Breaks" is not a "Depends"; it's more closely akin to a "Conflicts", which is basically the opposite of a "Depends". Michael Lange's reply summarizes this accurately. > That aside, python-tornado and python-zmq neither depends nor > conflicts with one another. It may be different for Stretch, though. As a side note, "Conflicts" and "Breaks" are both defined relationships for the apt package database, and they have different meanings. I don't remember offhand which meanings attach to which term, though. <snip> > So, where exactly python-zmq enters the picture, I don't know. Trying to figure that out would lead us back to the question: what exactly was the command which resulted in the original message you quoted? At a glance, I wouldn't expect that that message could ever appear unless a version of python-tornado which does have a Breaks: against 'python-zmq < 17' is being considered for installation. -- The Wanderer The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. -- George Bernard Shaw
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