Following up with a relevant link. https://ooktech.com/jed/ExampleWikis/FilterLogicExamples/
On Wednesday, August 26, 2020 at 8:22:48 PM UTC-4 TW Tones wrote: > Amreus, > > Filters are a little different to standard boolean logic since they start > from a premise of generating a list of tiddler titles > > The following is a quick and untested response, please experiment. > > In your example > [is[current]has[birt_date]] [is[current]has[birt_plac]] > The result will be two values (title of the current tiddler) if both > fields have a value, but since the value is the same, the current tiddler > title it will be de-duplicated to one tiddler title. > > Perhaps one could write this as > [(A!!B) or (A!!C)] where A is just a qualifier as to which B and which C > to use. The result returned will be blank for false or A for true. > > There are no parenthesis for order since the order is left to right. > Filters operate on the output of the previous step or each run is an AND. > [[title1]] [[Title2]] represents both two titles and two runs like > [prefix[title1]] [prefix[Title2]] and the results of both runs are joined > and de-duplicated > > In the Doco Maths https://tiddlywiki.com/#Mathematics%20Operators it > explains how to stop de-duplication for undertaking maths. > > Back to your original question > [{!!birt_date}] [{!!birt_plac}] will list the content of the fields if > they have a value, A is implicit in the "!!fieldname" > > You can also get the value of a field, if no value it will not return a > value > [is[current]get[birt_date]] [is[current]get[birt_plac]] > > but I'm not sure how to write [A and (B or C)] in filter. > > I think you already have? '[is[current]has[birt_date]] > [is[current]has[birt_plac]]' > However The Test for A is not really a test, just a reference to a > particular tiddler > > Personally I suggest learning the filter syntax from the angle of its > original purpose, titles, since tiddlers are the atomic unit in tiddlywiki, > you will then start to discover ways to emulate other logical operations. > > Some quick examples > [is[current]has[birt_date]has[birt_plac]] title returned only if they > both have a value > > [is[current]has[birt_date]] +[is[current]has[birt_plac]] title returned > only if first then second is true, the second is free to refer to anything > so you needs to specify current if thats what you want > > Rather than return the title you can now use then and else to set the > output > > [is[current]has[birt_date]then[yes]else[no]] > > Finally; > Remember with the list widget the output of a filter, if true or a list is > generated to apply it for each title to the contents of the list. > > Sometimes if the list is used to display content only we may use > +[limit[1]] so if anything satisfies the filter it will display the content > once. > > Regards > Tony > > > On Thursday, 27 August 2020 07:44:12 UTC+10, amreus wrote: >> >> Good evening. >> >> Just a question of curiosity. Can this filter be simplified? For >> example, can all[current] be "factored out" so it does not need to >> appear twice? >> >> [is[current]has[birt_date]] [is[current]has[birt_plac]] >> >> In Boolean, I think this would be [(A and B) or (A and C)] == [A and (B >> or C)], but I'm not sure how to write [A and (B or C)] in filter. >> > -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/tiddlywiki/7b8c6e78-9701-49fc-a3c1-18d556a55011n%40googlegroups.com.
