c - Does there exist an LR(k) grammar with no LL(1) equivalent -

-

i haven't been able find answer yet. there grammars context free , non-ambiguous can't converted ll(1)?

i found 1 production couldn't figure out how convert ll(1): parameter-type-list production in c99:

parameter-type-list:     parameter-list     parameter-list , ...

is example of lr(k) grammar doesn't have ll(1) equivalent or doing wrong?

edit: copied wrong name, meant copy parameter-declaration:

parameter-declaration:     declaration-specifiers declarator     declaration-specifiers abstract-declarator(opt)

the problem declarator , abstract declarator both having ( in first set, being left recursive.

in general, lr(k) grammars more powerful ll(k). means there languages lr(k) parser, not ll(k).

one of examples language defined grammar:

s -> s  s -> p p -> p b p -> \epsilon

or, in other words, string of a's, followed same or less number of b's. follows fact ll(k) parser must make decision every a encountered - paired b - looking ahead no more k symbols of input, can a's, giving no useful information. strict proof, @ second part of accepted answer here https://cs.stackexchange.com/questions/3350/is-this-language-ll1-parseable

your example, however, can left factored in ll(1) grammar be

parameter-type-list -> parameter-list optional-ellipsis optional-ellipsis -> \epsilon optional-ellipsis -> , ...

one note follow set parameter-list contain , character, , can cause first-follow conflict. if case, need see parameter-list definition fix conflict too.

edit: parameter-declaration rule seems complicated answer right away. can try perform left factorization hands conflicting alternatives, or assistance tool, antlr.


Comments

Post a Comment

Popular posts from this blog

qt - Using float or double for own QML classes -

-
i've created components , helper methods using c++ , qt used in qml gui. of methods calculate gui elements (size, transformations, scene graph items creation). target arm 32 bit using opengl / eglfs render output. opengl using float , qml using real (defined double ). what should use in c++ do not lose precision? if use qreal ( double ) shouldn't lose precision. if git grep float in qtbase.git , can find out bit more: dist/changes-5.2.0-**************************************************************************** dist/changes-5.2.0-* important behavior changes * dist/changes-5.2.0-**************************************************************************** dist/changes-5.2.0- dist/changes-5.2.0- - qt compiled qreal typedef'ed double on dist/changes-5.2.0: platforms. qreal float on arm chipsets before. guarantees more dist/changes-5.2.0- consistent behavior between platforms qt supports, binary dist/chan...
Read more

Create Outlook appointment via C# .Net -

-
i need create outlook appointment using microsoft.office.interop.outlook , while can work locally on own workstation , works if run web application via server's browser, not work when connect server externally. hence, think might permission issue. i changed application pool identity " localsystem " don't access denied error. unfortunately, doesn't work. the app behaves if appointment created, appointment doesn't appear in outlook. here include file on top of aspx.cs page using outlook = microsoft.office.interop.outlook; here code using pop appointment. outlook.application apptapp = new outlook.application(); outlook.appointmentitem appt = apptapp.createitem(outlook.olitemtype.olappointmentitem) outlook.appointmentitem; appt.subject = txtfirstname.text + " " + txtlastname.text; appt.body = txtcomment.text; appt.alldayevent = false; appt.start = datetime.parse(txtreminderdate.text + " 8:00 am"); appt.end = datetime.p...
Read more

ios - Swift Array Resetting Itself -

-
i have 2 arrays: pointhistory , datehistory . have nstimer , , when timer runs out, action called. in action appending int pointhistory , , current date string datehistory . here timer action: func timeraction() { let steppervalue = int(stepper.value) employee.numberofpoints = steppervalue networking.saveemployee(employee, completion: { (error) -> void in if error != nil { let alert = uialertcontroller(title: "error", message: "there error updating \(self.employee.name)'s points", preferredstyle: .alert) let alertaction = uialertaction(title: "ok", style: .cancel, handler: nil) alert.addaction(alertaction) self.presentviewcontroller(alert, animated: true, completion: nil) } }) var dateformatter = nsdateformatter() dateformatter.dateformat = "mm-dd-yyyy" dateformatter.timezone = nstimezone.localtimezone() var date = nsdate() var ...
Read more