Type annotations are used at compile time to generate direct method calls (as opposed to using reflection).
`cast` is a function, so it doesn't do anything until runtime, and it just delegates to Class#cast. I don't think it is used much. In the core, it's only called in single- arity cases for * and +, to make sure that the operand is indeed a Number. Not sure about the type inference here. Have you tried with SourceDataLine imported, but without the annotation? Rich does that in the example. On Jul 24, 10:53 pm, Kartik <ksara...@gmail.com> wrote: > Hello. I have the following code snippet to start reading an mp3 file > > (let [file (File. filename) > stream (AudioSystem/getAudioInputStream file) > base-format (.getFormat stream) > decoded-format (AudioFormat. AudioFormat$Encoding/ > PCM_SIGNED ...) > line-info (DataLine$Info. SourceDataLine decoded-format) > decoded-stream (AudioSystem/getAudioInputStream decoded-format > stream) > line (AudioSystem/getLine line-info) > buffer (byte-array (* 1024 4))] > (pprint line) > (.open line decoded-format) > (.start line) > ...) > > This works fine on Mac OSX. The pprint gives > > #<MixerSourceLine com.sun.media.sound.MixerSourceLine@56101751> > > When I run it in windows I get > > Can't call public method of non-public class: public void > com.sun.media.sound.AbstractDataLine.open(javax.sound.sampled.AudioFormat) > throws javax.sound.sampled.LineUnavailableException > [Thrown class java.lang.IllegalArgumentException] > > This time the pprint gives > > #<DirectSDL com.sun.media.sound.DirectAudioDevice$DirectSDL@173bb67> > > The problem is that getLine on windows returns DirectSDL which is a > private inner class of DirectAudioDevice. I tried casting it to > SourceDataLine which is the type I need (which is a literal > translation of equivalent java code I'm following) by doing > > line (cast SourceDataLine (AudioSystem/getLine line-info)) > > But that didn't work. I had to declare the type like so > > #^SourceDataLine line (AudioSystem/getLine line-info) > > My question is what is the difference between casting and type > declaration? Why does one work and not the other in this case? In > general, when is one used over the other? > > I found a related post from > Richhttp://www.mail-archive.com/clojure@googlegroups.com/msg13283.html > where he says the let (without type declaration I assume) should allow > the compiler to infer the type. > > Thanks > > Kartik -- 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
