Nice, Mike. I stole your work and put it into the Wiki I created to see how it fit:
http://clojure-examples.appspot.com/clojure.core/reduce (Note: reduce seems to be missing a doc string in 1.2 master; for other functions doc strings show up.) As cool as walton is, it's kind of a firehose. A curated collection of examples (perhaps pilfering from walton and others) would be more valuable, I think. Justin On Jul 2, 2:58 pm, Mike Meyer <mwm-keyword-googlegroups. 620...@mired.org> wrote: > On Fri, 2 Jul 2010 07:50:45 -0700 (PDT) > > Meikel Brandmeyer <m...@kotka.de> wrote: > > On Jul 2, 12:18 pm, Walter van der Laan <waltervanderl...@gmail.com> > > wrote: > > > For example you can point your browser > > > athttp://getclojure.org:8080/examples/reduce > > > for reduce examples. > > Is it necessary to have >250 examples for a function which has > > effectively five variations? > > (reduce + []) > > (reduce + [1]) > > (reduce + [1 2 3]) > > (reduce + 0 []) > > (reduce + 0 [1 2 3]) > > Seconded. > > > I'm all for examples, but please: clear examples focusing on the thing > > being demonstrated. Symbol calling or showing that [1 2 3] and (list 1 > > 2 3) can be interchanged in the example above are nice to know, but > > don't help to understand reduce itself. They should go to their own > > sections in a tutorial. > > Yes. Symbol calling and the equivalence of [1 2 3] and '(1 2 3) aren't > really relevant to what reduce can do. Nor is showing someone how to > extract the arglist from a functions metadata. > > While I think the effort is marvelous, some thought should go into the > purpose. That page looks like the purpose is to show off the > cleverness of the person who wrote it. As such, this page is probably > more confusing than helpful. > > > PS: I also think the examples should demonstrate idiomatic clojure. [1 > > 2 3] is idiomatic while '(1 2 3) is not. Whatever we put in examples > > will show up in code. So be it [] vs. '() or (.java interop) vs. (. > > interop (java)) - we should pay attention! > > Ditto. > > Examples are read in order, and should be presented from simple to > more complex. In particular, the first example shouldn't require > knowing anything but clojure syntax. Each further example should > introduce at most one new concept, reinforce the previous example > (though that should be kept to a minimum), or show the function > working on different data types - if they're not doing one of those > things, why are they there? All the inputs to an example should be > either literals, or the result of a simple function invocation. If the > user has to work to figure out what the input is, they're that much > more likely to skip the example, or - even worse - come up with the > wrong input and hence wrong result. Finally, maybe provide one example > (short) that might be considered a "real world" use. > > They really need to include an explanation. Having the expected > results there would be nice as well. > > > The 0.02€ of a guy who has not put effort in creating examples for the > > core API. > > Not wanting to be that guy (no offense intended to Meikel, he made a > good point), here's what I think is a nice set of reduce examples: > > ; sum of 0 through 10: 45 > (reduce + (range 10)) > > ; Divide 1 by 2 and then 3: 1/6 > (reduce / 1 [2 3]) > > ; Build a set from a collection: #{:a :c :b} > (reduce conj #{} [:a :b :c]) > > ; Build a sorted set from multiple collections: #{1 2 3 4 5 6} > (reduce into (sorted-set) [[3 1 2] [5 4 6]]) > > ; Reverse a list: (3 2 1) > (reduce #(cons %2 %1) [] [1 2 3]) > > ; Build a hash-map from n to n squared: > ; {0 0, 1 1, 2 4, 3 9, 4 16, 5 25, 6 36, 7 49, 8 64, 9 81} > (reduce #(assoc %1 %2 (* %2 %2)) {} (range 10)) > > ; Edge case with one argument: returns argument -> 2 > (reduce conj [2]) > > ; Edge case with one argument: returns argument -> 1 > (reduce conj 1 []) > > ; Note that in the previous two examples, conj is not invoked, as it > ; always returns a sequence. > > ; Edge case with no arguments: (*) -> 1 > (reduce * []) > > ; Broken edge case: Wrong number of arguments passed to function: > (reduce conj []) > > -- > Mike Meyer <m...@mired.org> http://www.mired.org/consulting.html > Independent Network/Unix/Perforce consultant, email for more information. > > O< ascii ribbon campaign - stop html mail -www.asciiribbon.org -- 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
