Venkatesan S svtesan@gmail.com writes:

Olof-joachim, iterate-devel: Thanks for the help.

np :)

I have written a small driver for iterate which iterates over dates in a given range. The basic usage is: (iter (for (y m d) from-date '(2011 1 26) to '(2011 2 27) by 2 skipweekends nil)     (format t "~a/~a/~a~%" d m y))

notes:

1. default value for "to"  is today
2. default value for "by" is 1
3. skipweekends if true, skips over weekends

In the iterate driver, I would like to reuse the given variables (y m d) instead of gensym'ming , but I get a slew of errors, which I am unable to comprehend.

Well, using something other than a plain symbol after the FOR keyword isn't supported by DEFMACRO-DRIVER because that symbol is inserted in a normal macro definition. E.g.:

(macroexpand '(defmacro-driver (FOR (a b c d) FROM-DATE from-date-spec) ...))

expands to something like (minus some other things):

(DEFMACRO CLAUSE-FOR-FROM-DATE... (&KEY ((:FOR A) B C D) ...)) ...)

which isn't exactly legal[1] even if SBCL doesn't warn here for macro definitions.

Instead, the return value of the generator code can be destructured by the user like in your example above. But that part is separated from the generator and you can't hook into it unless you want to use some internal functionality from iterate.

Is it worth the hassle? If so, I've attached a somewhat working rewrite based on some experimentation. It's not finished, I've only transcribed from your code and it works for me (tm).

I would like to include this in date-calc package, as I feel it logically belongs there. Please let me know how to go about this.  I am just learning lisp, and all comments/flames are welcome.

Well, contact the author? And although it may for you logically belong there, it adds a dependency to the date-calc package, which is, for a small library perhaps not worth it. Since iterate has contribs (or one, the postgres driver) I'd think it could be added there instead more easily. But I'm only using this library, so same goes here.

Code remarks: I'd probably use &key instead of &optional, because wrapping date-calc:today every time I want to change skip-weekends would be too much work. Everything else is personal style, such as my habit for long names. And for just learning it looks good, imho.

General remarks: use irc.freenode.net, #lisp and, if you like usenet, comp.lang.lisp, because there're certainly more people reading in those places. And you'll get more flames ;)

Cheers, Olof

[1]: http://www.lispworks.com/documentation/HyperSpec/Body/03_dd.htm

--8<---------------cut here---------------start------------->8--- (iterate::defclause-driver (FOR year-month-date-vars FROM-DATE from-date-spec &optional TO to-date-spec BY (n 1) SKIP-WEEKENDS (skipval t)) "Driver for iterating over dates. All dates are in (YYYY MM DD) format." (declare (ignorable to-date-spec)) (iterate::top-level-check) (unless (and (listp year-month-date-vars) (every #'symbolp year-month-date-vars)) (iterate::clause-error "~a should be a list of up to three variables: ~ the year, month and day" year-month-date-vars)) (mapc #'iterate::make-default-binding year-month-date-vars) (let* ((step-var (iterate::make-var-and-default-binding 'by :type 'fixnum)) (fy (iterate::make-var-and-default-binding 'from-year :type 'fixnum)) (fm (iterate::make-var-and-default-binding 'from-month :type 'fixnum)) (fd (iterate::make-var-and-default-binding 'from-day :type 'fixnum)) (ty (iterate::make-var-and-default-binding 'to-year :type 'fixnum)) (tm (iterate::make-var-and-default-binding 'to-month :type 'fixnum)) (td (iterate::make-var-and-default-binding 'to-day :type 'fixnum)) (step `((multiple-value-setq (,fy ,fm ,fd) (get-next-day ,fy ,fm ,fd ,step-var ,skipval)) (multiple-value-setq ,year-month-date-vars (values ,fy ,fm ,fd)))) (test `(when (< (date-calc:delta-days ,fy ,fm ,fd ,ty ,tm ,td) 0) (go ,iterate::*loop-end*)))) (setf iterate::*loop-end-used?* T) (iterate::return-driver-code :initial `((setq ,step-var ,n) (destructuring-bind (y m d) ,from-date-spec (multiple-value-setq (,fy ,fm ,fd) (get-next-day y m d (- ,step-var) ,skipval))) (let ((spec ,to-date-spec)) (multiple-value-setq (,ty ,tm ,td) (if spec (values-list spec) (date-calc:today))))) :next `(,.step ,test) :variable year-month-date-vars))) --8<---------------cut here---------------end--------------->8---