-1 from me. First of all, it's hard to understand what it does and to read it later. Also, => is Lambda notation in JS/C# and people from these languages will be very confused about it.
On Thu, Jan 26, 2017 at 12:06 PM Remi Forax <fo...@univ-mlv.fr> wrote: > The other problem i see is that the fat arrow => is used by several > mainstream languages ; C#, Scala, JavaScript at least ; for declaring a > lambda. > This will confuse people in my opinion. > > Moreover as Jochen said , implies is a lazy operator, like && and ||, so > the operator should be more =>=> than => (i.e !a || b vs !a | b). > Also if there is a method 'implies' as there is a method 'plus', implies > should take a closure and not the result of an expression. > At that point, the question is whenever or not to also implement && and || > as method and has a general 'lift' syntax when declaring a method, it will > make simple macro far easier to write at the expense of more magic. > > Rémi > > ------------------------------ > > *De: *"Guillaume Laforge" <glafo...@gmail.com> > *À: *dev@groovy.apache.org > *Cc: *"Groovy_Developers" <d...@groovy.incubator.apache.org> > *Envoyé: *Jeudi 26 Janvier 2017 10:33:21 > *Objet: *Re: 答复: About the "implies" operator(GROOVY-2576) > > I'm not super convinced either, and I'm wondering when I'd really use such > an operator. > I'm kinda +0 as Cédric here. > > Not that we should copy or not other languages, but are there others that > have such an operator, and if this is the case, do we know how (much) it's > used? > > On Thu, Jan 26, 2017 at 10:22 AM, Cédric Champeau < > cedric.champ...@gmail.com> wrote: > > I know it's well known in mathematical logic, but I don't want Groovy to > become Scalaz either. The route is dangerous. > > 2017-01-26 10:18 GMT+01:00 Daniel Sun <realblue...@hotmail.com>: > > Hi Cédric, > > > > Here is the background of the “implies” operator, which is well > known in the mathematical logic 😉 > > http://mathworld.wolfram.com/Implies.html > > > > > > *发件人: *[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5738105&i=0> > *发送时间: *2017年1月26日 17:12 > *收件人: *[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5738105&i=1> > *主题: *Re: About the "implies" operator(GROOVY-2576) > > > I'm not convinced we should add more operators. Honestly, I had to read > the description of the "implies" operator to understand what it does. This > is clearly not the case for || or &&, which are "well known" operators. > > I am also worried about code becoming ascii art: > > { a -> a => a <= c => d } > > So I'm just +0, I don't see that I would use it often enough to mitigate > the drawbacks. > > 2017-01-26 1:47 GMT+01:00 Daniel Sun <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5738104&i=0>>: > Hi Jochen, > > Thanks for your analysis in detail :) > > => is a very expressive operator. if we could implement it as > +(corresponding to plus method) does and apply different business logic > when necessary, it would be much more useful. And the default > implementation of "implies" method can be "!a||b". > > As to the association of the operator, I prefer the left > association, i.e. a => b => c is equivalent to (a => b) => c. > > The above is the initial plan to implement the "implies" operator. > > Cheers, > Daniel.Sun > > > 在 2017年1月26日 上午3:20，"Jochen Theodorou [via Groovy]" > <ml-node+s329449n5738042h6 > On 25.01.2017 17:50, Daniel Sun wrote: > > > Hi all, > > > > The "implies" operator "=>" was suggested many years ago, here is > the > > replated JIRA issue( GROOVY-2576 > > <https://issues.apache.org/jira/browse/GROOVY-2576> ) . > > > > Do you want it for Groovy 3? (+1: yes; -1: no; 0: not bad) > > > > BTW, recently I have been going through the issues related to the > old > > parser, many issues existing for many years do not exist in the new > parser > > Parrot :) > > If we do this (and I say +1) we should clear some things: > 1) what does a=>b=>c mean, since (a=>b)=>c is not the same as a=>(b=>c) > 2) use groovy truth and when to apply it? If we map a=>b to !a||b, then > it will use Groovy truth on a and b, but if we map to an implies method > it will get a and b, use groovy truth on them or not and we then maybe > use groovy truth on the result. I personally would be for not using > groovy truth here, thus make it more in line with | and &. > 3) if a=>b is mapped to !a||b we will evaluate a, negate it, and > depending on the result maybe never evaluate b. As long as a and b are > free of side effects, that does not play an extremely important role, > but if we map it to a method a and b will be evaluated always. If we > would say it is more like !a|b, which would also require both being > evaluated, then there is still the fact that !a ensures we call here > always the boolean or function, never one defined by an arbitrary a > 4) instead of using !a, which converts a to a boolean and negates it, we > can also use ~a, which is a binary negate also working on booleans, but > not converting a to a boolean if it is no boolean. Here we have to > especially think about ~a|b calling "or" on a Pattern if a is a String. > Also not many things besides boolean and numbers really support > something useful of the binary negate. > > I mention those points so we can make a proper specification for the > behaviour of this operator ;) > > bye Jochen > > > ------------------------------ > If you reply to this email, your message will be added to the discussion > below: > > http://groovy.329449.n5.nabble.com/About-the-implies-operator-GROOVY-2576-tp5738035p5738042.html > To unsubscribe from About the "implies" operator(GROOVY-2576), click here. > NAML > <http://groovy.329449.n5.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> > > ------------------------------ > View this message in context: Re: About the "implies" > operator(GROOVY-2576) > <http://groovy.329449.n5.nabble.com/About-the-implies-operator-GROOVY-2576-tp5738035p5738043.html> > > Sent from the Groovy Dev mailing list archive > <http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html> at > Nabble.com. > > > > ------------------------------ > If you reply to this email, your message will be added to the discussion > below: > > http://groovy.329449.n5.nabble.com/About-the-implies-operator-GROOVY-2576-tp5738035p5738104.html > To unsubscribe from About the "implies" operator(GROOVY-2576), click here. > NAML > <http://groovy.329449.n5.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> > > ------------------------------ > View this message in context: 答复: About the "implies" > operator(GROOVY-2576) > <http://groovy.329449.n5.nabble.com/About-the-implies-operator-GROOVY-2576-tp5738035p5738105.html> > > Sent from the Groovy Dev mailing list archive > <http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html> at > Nabble.com. > > > > > > -- > Guillaume Laforge > Apache Groovy committer & PMC Vice-President > Developer Advocate @ Google Cloud Platform > > Blog: http://glaforge.appspot.com/ > Social: @glaforge <http://twitter.com/glaforge> / Google+ > <https://plus.google.com/u/0/114130972232398734985/posts> > >
