Re: [rules-dev] else

For further info, this is what ilog do. They only allow an implicit "else" on the last "evaluate" expression. Which while simple is quite restrictive.: http://publib.boulder.ibm.com/infocenter/brjrules/v7r1/index.jsp?topic=/c... rule ruleName { when {conditioni evaluate (expression)} then {[action1 ... actionm]} else {[action1 ... actionp]} }; OPSJ is the only engine that i know of that uses labels: x.name == obj, x.weight == "light", x.location != g.location); mky: monkey; [4] (mky.holds == obj); } do { makegoal("walkto", loc); } else( 4 ) { makegoal("holds", obj); } Although I would encourage people to think beyond simple "if/else", the proposal I put forward would allow for tree like data flows for signal processing - which will map very nicely to GUI tooling. Mark On 19/08/2011 13:56, Toni Rikkola wrote: I got the same feeling that Geoffrey had about readability. We added "from" its really easy to get, why not add "else". when Person( name == "darth" ) else [darthIsMissing] A() then .... then.darthIsMissing log("Darth was never found"); end or when Person( name == "darth" ) else { log("Darth was never found"); } A() then .... end "Inline then" could be done with inner rules. Similar to what Mario suggested. rule "Handle Login" when $loginRequest :LoginRequest() AuthorizedUsers( list contains $loginRequest.user ) else [unsuccessfulLoginAttempt] inner rule "Check if Admin" $p :AdminRights( user == $loginRequest.user ) then showAdminMenu(); end then logInUser( $loginRequest.user ); then.unsuccessfulLoginAttempt log( "There was and unsuccessful login attempt with the user name " + $ loginRequest.user.name ); end Toni On Aug 19, 2011, at 2:59 PM, Geoffrey De Smet wrote: I like Mario's proposal because I can actually read it. Those special chars | < are gibberish to me. The only reason we're not debating to use a new readable, intuitive keyword, is because of the back-wards compatibility issues involved. But using unreadable, unintuitive special char just for that, is probably not a good idea. I wonder if we reserve new keywords by prefix them with reserved special char like "@"? Then we can introduce as many keywords as we want without breaking backwards compatibility. Who's our target users for DRL authors? A) Supersmart computer science guys B) Blue collar Java programmers C) Domain experts (= not programmers) I 'd classify "{notA} < A()" as (given some time to learn it) readable for A, but not for B and C. Op 18-08-11 23:35, Mario Fusco schreef: Hi Mark, Since you're gathering 2 cents here and there I decided to add also mine even if I am pretty sure that I am still missing the whole picture and anyway at the moment I cannot see all the consequences of what I am going to propose. To tell you the truth I find the label syntax not very intuitive and I was wondering if we could avoid it in some way. In the end what the 90% of the users are asking for is just something like: rule R when A() then do something else do something else end while we are going to give them something that is not exactly the same: rule R when {notA} < A() then do something then.notA do something else end In particular I was thinking if we could keep the when ... then ... else syntax that should be familiar to the biggest part of the users and at the same time obtain a flexibility similar to the one provided by the labels syntax. Probably we could do it with a kind of nested rules so, for instance, the rule: rule R1 when {af} < A() > {at} B() then DO then.af DO.af then.at DO.at end could be rewritten as it follows: rule R1 when B() then DO rule R1A when A() then DO.at else DO.af end end Of course the nested rule couldn't be used by the Drools engine as it is, but we could implement a kind of "linearization" process at compile time that translates it more or less as: rule R1_1 when A() B() then DO DO.at end rule R1_2 when not A() B() then DO DO.af end In the same way the "or" example: rule R1 when ( A() > {a1} or B() > {b1} or C() > {c1} ) D() then DO then.a1 DO.a1 then.b1 DO.b1 then.c1 DO.c1 end could be written as: rule R1 when D() then DO rule R1A when A() then DO.a1 end rule R1B when B() then DO.b1 end rule R1C when C() then DO.c1 end end and then linearized at compile time in a similar way as I wrote before. Once again I still haven't evaluated all the implications of my suggestion neither I know if we can cover with it all the cases proposed by Mark. I am pretty sure I am missing something important to be honest, but since we are in a "brainstorming phase" I thought it could worth to consider it at least. My 2 cents, Mario _______________________________________________ rules-dev mailing listrules-dev@lists.jboss.orghttps://lists.jboss.org/mailman/listinfo/rules-dev -- With kind regards, Geoffrey De Smet _______________________________________________ rules-dev mailing list rules-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-dev _______________________________________________ rules-dev mailing listrules-dev@lists.jboss.orghttps://lists.jboss.org/mailman/listinfo/rules-dev _______________________________________________ rules-dev mailing list rules-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-dev