Thanks Mauricio ... I think I understand it now. Regards, Kashyap On Monday, January 13, 2014 9:48:28 PM UTC+5:30, Mauricio Aldazosa wrote: > > > > On Mon, Jan 13, 2014 at 8:49 AM, Kashyap CK <ckka...@gmail.com<javascript:> > > wrote: > >> >> I'd really appreciate it if someone could tell me what's going on when I >> do the following - >> >> user> (defn xx [] (map println [1 2 3 4 5 6])) >> #'user/xx >> user> (take 2 (xx)) >> (1 >> 2 >> 3 >> 4 >> 5 >> 6 >> nil nil) >> user> >> > > There are many things that you need to be aware of here: > > 1. Lazy seqs are chunked. As an optimization they are realized 32 > elementes at a time. There are ways to go around this: > http://blog.fogus.me/2010/01/22/de-chunkifying-sequences-in-clojure/ > 2. map returns a lazy seq of the return value of the function it uses, > and println returns nil as a result. > 3. Lazy seqs and IO usually are a confusing mix. > > So, as a result of chunking a println for all six elements is made. Each > of this calls, as a side effect prints the number and, returns nil. Then > you ask for the first two return values of that sequence, hence the "nil > nil". Everything is getting mixed up at the repl so it seems confusing, but > the result of xx is (nil nil) and the side-effect of it is the printing of > 1 2 3 4 5 6. > Cheers, > Mauricio >
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