tagbody vs. defun
in [Lisp]
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From: John Thingstad on 27 Oct 2009 12:57 Den Tue, 27 Oct 2009 12:46:41 -0400, skrev xach: > Willem Broekema <metawilm(a)gmail.com> writes: > >> On 27 okt, 17:17, Bigos <ruby.obj...(a)googlemail.com> wrote: >>> There's one thing that puzzles me most. What is best practice to group >>> several functions together? For example in body of a loop. >>> >>> (dotimes (x 3) >>> (tagbody >>> (format t "one ~a~%" x ) >>> (format t "two ~a~%" x) >>> (format t "three ~a~%" x) ) ) >> >> PROGN is what you're looking for, though DOTIMES has an implicit PROGN >> so in this example you don't need a grouping statement. > > Actually, DOTIMES (and some other constructs) have an implicit TAGBODY, > not an implicit PROGN. > > Zach Yes, looping constructs generally use tagbody and go under the hood. (This might be a good time to look into 'macroexpand') Also I feel I should mention that the tagbody here is redundant, it doesn't need a progn either.
From: Pillsy on 27 Oct 2009 14:48 On Oct 27, 12:50 pm, Bigos <ruby.obj...(a)googlemail.com> wrote: > On 27 Oct, 16:31, Willem Broekema <metaw...(a)gmail.com> wrote: [...] > thanks everyone the code below does the trick, later I will also check > dotimes > (progn > (format t "one~%") > (format t "two~%") > 3 ) I'm going to second Tamas' advice about reading a Common Lisp book at this point. Since you have experience programming in other languages, I think _Practical Common Lisp_, available at http://www.gigamonkeys.com/book/, is the best choice. PROGN and TAGBODY both have their place, but PROGN is needed pretty rarely and I can count the number of times I've used TAGBODY on my thumbs. A decent book[1] will make the differences clear and put you well on your way to writing idiomatic CL. Cheers, Pillsy [1] PCL is excellent; its only shortcoming IMO is its lack of exercises.
From: Bigos on 27 Oct 2009 15:40 > I'm going to second Tamas' advice about reading a Common Lisp book at > this point. Since you have experience programming in other languages, > I think _Practical Common Lisp_, available athttp://www.gigamonkeys.com/book/, > is the best choice. PROGN and TAGBODY both have their place, but PROGN > is needed pretty rarely and I can count the number of times I've used > TAGBODY on my thumbs. A decent book[1] will make the differences clear > and put you well on your way to writing idiomatic CL. > > Cheers, > Pillsy > > [1] PCL is excellent; its only shortcoming IMO is its lack of > exercises. I have read first 3 chapters. But the problem is, I can't learn while staring at the book. I need to experiment, and feel how things work.Perhaps, as you say, the book would be better with some exercises. Without help from the list I wouldn't know what to look for, so I'm very grateful for your assistance. now googling for: progn site:http://www.gigamonkeys.com gives me information I need. Now I'm going back to reading the book, then will experiment a bit, and if I'm stuck I will post something again.
From: Slobodan Blazeski on 27 Oct 2009 16:03 On Oct 27, 5:17 pm, Bigos <ruby.obj...(a)googlemail.com> wrote: > There's one thing that puzzles me most. What is best practice to group > several functions together? For example in body of a loop. > > (dotimes (x 3) > (tagbody > (format t "one ~a~%" x ) > (format t "two ~a~%" x) > (format t "three ~a~%" x) ) ) > > Is tagbody the right way to do it or even for one loop I need to > define a function. > > (defun mytagbody (x) > (format t "one ~a~%" x ) > (format t "two ~a~%" x) > (format t "three ~a~%" x)) > (dotimes (x 3) > (mytagbody x)) > > I am puzzled because in Lisp code I have seen so far I didn't see > tagbody being being used, although in other languages there are > constructs to group statements together. As other posters stated you don't need a grouping statement (dotimes (x 3) (format t "one ~a~%" x) (format t "two ~a~%" x) (format t "three ~a~%" x)) However every time you write blockish code like above there's a big chance you're doing something odd. How about below: (dotimes (x 3) (mapc (lambda (s) (format t s x)) '("one ~a~%" "two ~a~%" "three ~a~%"))) cheers Bobi
From: xach on 27 Oct 2009 16:11
Slobodan Blazeski <slobodan.blazeski(a)gmail.com> writes: > However every time you write blockish code like above there's a big > chance you're doing something odd. How about below: > (dotimes (x 3) > (mapc (lambda (s) (format t s x)) > '("one ~a~%" "two ~a~%" "three ~a~%"))) That is pretty odd too. What about this? (dotimes (x 3) (dotimes (y 3) (format t "~R ~D~%" (1+ y) x))) Zach |