I don't think I like the notion of a lazy-seq and an iterator, since reading the iterator also changes it. Consider the case where you create a lazy-seq from an iterator, and the iterator somehow escapes. Somewhere else the iterator is read from, and now the data that where supposed to be in the lazy-seq no longer exists.
I guess you could clone the iterator, but that would sort of remove the purpose of using a lazy-seq in the first place. Jonathan On Sat, Jul 9, 2011 at 3:17 PM, David Powell <djpow...@djpowell.net> wrote: > > On Sat, Jul 9, 2011 at 10:10 AM, stu <stuart.hungerf...@gmail.com> wrote: > >> Hi, >> >> I'd like to make use of Java classes implementing the Java2D >> PathIterator interface: >> >> >> http://download.oracle.com/javase/6/docs/api/java/awt/geom/PathIterator.html >> >> Which leads to a serious impedance mismatch between immutable Clojure >> data structures and the iterator's approach of calling next() until >> isDone() and using currentSegment() to retrieve the point >> coordinates. >> >> I'd guess this kind of iterator is widely used in the Java world, so >> can some kind person point to an example of Clojure code using a Java >> iterator in this way? >> >> Thanks in advance, >> >> Stu >> > > Clojure has a built in function, iterator-seq, which converts a > java.util.Iterator to a lazy-seq. Lazy-seq's keep a copy of each data item > that they have grabbed from the iterator, so they hide the mutability of > Iterators. > > http://clojuredocs.org/clojure_core/clojure.core/iterator-seq > > Your interface doesn't subclass java.util.Iterator though, so you would > need to make something similar. > > I haven't tested this, but maybe something like this: > > > (defn pathiterator-seq > [i] > (when-not (.isDone i) > (lazy-seq > (.next i) > (let [arr (make-array Double/TYPE 6) > type (.currentSegment i arr)] > (cons {:type type :coords (into [] arr)} > (pathiterator-seq i)))))) > > > -- > Dave > > > -- > 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 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
