Both `for` and `doseq` support the same vector form preceding a body. `for` returns a lazy sequence and is often appropriate for a purely functional body. `doseq` is not lazy and returns nil, so it is only appropriate when you want to run the body for side effects.
Take a look at http://clojure.github.io/clojure/clojure.core-api.html and play around in the repl to get a clearer idea of how that works. Maybe start with an expression like this: (let [nested [[1 2 3] [4 5 6]]] (for [row nested number row] (str number " from row " row))) If you change `for` to `doseq`, you may also want to change `str` to `println`. Alan's example uses `map-indexed` to get numeric indices. Note that `cols` holds a row from `rows` and is then passed to the second `map-indexed` call, so his example is like a nested for-loop in a C-like language, except that it is lazy and returns a sequence of results of calling `display` with each item from your nested vector along with its coordinates. For this example to make sense, `display` should return a value that will be used to put something on screen. If `display` just does the screen-putting, and its return value is insignificant, then `doseq` would make sense. Hope this helps. -hume. On Apr 19, 2013 4:27 AM, <edw...@kenworthy.info> wrote: > How does that work: you appear to be iterating over two, unconnected, > vectors. > > And yes that's an example of the second option but doesn't explain if or > why that's the best approach- which was the question ;) > > On Thursday, 18 April 2013 19:48:40 UTC+1, Alan Malloy wrote: >> >> (for [[y cols] (map-indexed vector rows) >> [x cell] (map-indexed vector cols)] >> (display cell y x)) >> >> ? >> >> On Thursday, April 18, 2013 3:14:19 AM UTC-7, edw...@kenworthy.infowrote: >>> >>> So, I want a 2 dimensional array. >>> >>> I think the best way to implement this is a vector of vectors. >>> >>> Now I want to display that array drawing each element relative to its >>> position in the array. >>> >>> Is the best way to use doseq and manually maintain the indices? Or is it >>> to use nested for-loops manually iterating of the vector-of-vectors? >>> >> -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
