unexpected NaN behavior
Can someone explain the last result here? [1 2 3 Float/NaN] [1 2 3 NaN] (= Float/NaN Float/NaN) false (#(= Float/NaN Float/NaN)) false ; all is good so far, but... (filter #(= % %) [1 2 3 Float/NaN 4]) (1 2 3 NaN 4) Now I'm lost. What just happened? -- 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
Re: unexpected NaN behavior
Possibly a simpler example: user= (def x Float/NaN) #'user/x user= (= x x) true I'm not sure whether true or false makes more sense, personally. Wes On Tue, Oct 9, 2012 at 4:38 PM, Brian Craft craft.br...@gmail.com wrote: Can someone explain the last result here? [1 2 3 Float/NaN] [1 2 3 NaN] (= Float/NaN Float/NaN) false (#(= Float/NaN Float/NaN)) false ; all is good so far, but... (filter #(= % %) [1 2 3 Float/NaN 4]) (1 2 3 NaN 4) Now I'm lost. What just happened? -- 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
Re: unexpected NaN behavior
Float/NaN must be instantiating something? user= (def y Float/NaN) #'user/y user= (= x y) false On Tue, Oct 9, 2012 at 4:48 PM, Wes Freeman freeman@gmail.com wrote: Possibly a simpler example: user= (def x Float/NaN) #'user/x user= (= x x) true I'm not sure whether true or false makes more sense, personally. Wes On Tue, Oct 9, 2012 at 4:38 PM, Brian Craft craft.br...@gmail.com wrote: Can someone explain the last result here? [1 2 3 Float/NaN] [1 2 3 NaN] (= Float/NaN Float/NaN) false (#(= Float/NaN Float/NaN)) false ; all is good so far, but... (filter #(= % %) [1 2 3 Float/NaN 4]) (1 2 3 NaN 4) Now I'm lost. What just happened? -- 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
Re: unexpected NaN behavior
I every language I'm familiar with NaN tests unequal to all values, including itself. That's almost the definition of NaN. This looks like some kind of shortcut where clojure is not bothering to test equality of a symbol with itself. On Tuesday, October 9, 2012 1:48:54 PM UTC-7, Wes Freeman wrote: Possibly a simpler example: user= (def x Float/NaN) #'user/x user= (= x x) true I'm not sure whether true or false makes more sense, personally. Wes On Tue, Oct 9, 2012 at 4:38 PM, Brian Craft craft...@gmail.comjavascript: wrote: Can someone explain the last result here? [1 2 3 Float/NaN] [1 2 3 NaN] (= Float/NaN Float/NaN) false (#(= Float/NaN Float/NaN)) false ; all is good so far, but... (filter #(= % %) [1 2 3 Float/NaN 4]) (1 2 3 NaN 4) Now I'm lost. What just happened? -- You received this message because you are subscribed to the Google Groups Clojure group. To post to this group, send email to clo...@googlegroups.comjavascript: Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+u...@googlegroups.com javascript: 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
Re: unexpected NaN behavior
2012/10/10 Wes Freeman freeman@gmail.com Float/NaN must be instantiating something? See http://stackoverflow.com/a/1573715/1367685 and replies to it. NaN (and floating-point numbers in general) are tricky beasts. You get the same behavior in Scala and Java: scala Float.NaN == Float.NaN res1: Boolean = false -- MK http://github.com/michaelklishin http://twitter.com/michaelklishin -- 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
Re: unexpected NaN behavior
On Tue, Oct 9, 2012 at 4:38 PM, Brian Craft craft.br...@gmail.com wrote: Can someone explain the last result here? [1 2 3 Float/NaN] [1 2 3 NaN] (= Float/NaN Float/NaN) false (#(= Float/NaN Float/NaN)) false ; all is good so far, but... (filter #(= % %) [1 2 3 Float/NaN 4]) (1 2 3 NaN 4) Now I'm lost. What just happened? The behavior is strange, I've simplified it a bit to the following: ((fn [x] (= x x)) Float/NaN) true ((fn [x y] (= x y)) Float/NaN Float/NaN) false This is using Clojure 1.4.0 -- 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
Re: unexpected NaN behavior
On Tue, Oct 9, 2012 at 5:20 PM, David Nolen dnolen.li...@gmail.com wrote: On Tue, Oct 9, 2012 at 4:38 PM, Brian Craft craft.br...@gmail.com wrote: Can someone explain the last result here? [1 2 3 Float/NaN] [1 2 3 NaN] (= Float/NaN Float/NaN) false This is a primitive comparison and follows IEEE floating point semantics. NaN must not equal NaN. ; all is good so far, but... (filter #(= % %) [1 2 3 Float/NaN 4]) (1 2 3 NaN 4) This is an Object comparison, and in Java this follows the contract for equals and hashCode. Thus, an object must be equal to itself (for HashMap to work). See: http://stackoverflow.com/questions/1408569/why-does-double-nan-equal-itself-when-wrapped-in-a-double-instance and in particular: http://docs.oracle.com/javase/6/docs/api/java/lang/Double.html#equals(java.lang.Object) Now I'm lost. What just happened? The behavior is strange, I've simplified it a bit to the following: ((fn [x] (= x x)) Float/NaN) true ((fn [x y] (= x y)) Float/NaN Float/NaN) false This is using Clojure 1.4.0 -- 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
Re: unexpected NaN behavior
On Tuesday, October 9, 2012 2:27:43 PM UTC-7, Aaron Cohen wrote: On Tue, Oct 9, 2012 at 5:20 PM, David Nolen dnolen...@gmail.comjavascript: wrote: On Tue, Oct 9, 2012 at 4:38 PM, Brian Craft craft...@gmail.comjavascript: wrote: Can someone explain the last result here? [1 2 3 Float/NaN] [1 2 3 NaN] (= Float/NaN Float/NaN) false This is a primitive comparison and follows IEEE floating point semantics. NaN must not equal NaN. ; all is good so far, but... (filter #(= % %) [1 2 3 Float/NaN 4]) (1 2 3 NaN 4) This is an Object comparison, and in Java this follows the contract for equals and hashCode. Thus, an object must be equal to itself (for HashMap to work). See: http://stackoverflow.com/questions/1408569/why-does-double-nan-equal-itself-when-wrapped-in-a-double-instance and in particular: http://docs.oracle.com/javase/6/docs/api/java/lang/Double.html#equals(java.lang.Object) Thanks for the explanation. I notice by experimentation that == behaves as I would expect. I haven't actually found == in the docs. Only =. -- 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
Re: unexpected NaN behavior
I guess it really does do the same thing in Scala: scala val f = Float.NaN f: Float = NaN scala f == f res4: Boolean = false scala f.equals(f) res5: Boolean = true I guess you really should use == in Clojure, when doing numerical equality. It even does dynamic typed comparisons better than =. Such as: user= (= (/ 100M 100M) 1) false user= (== (/ 100M 100M) 1) true Thanks for clearing that up, Aaron. Wes On Tue, Oct 9, 2012 at 5:27 PM, Aaron Cohen aa...@assonance.org wrote: On Tue, Oct 9, 2012 at 5:20 PM, David Nolen dnolen.li...@gmail.com wrote: On Tue, Oct 9, 2012 at 4:38 PM, Brian Craft craft.br...@gmail.com wrote: Can someone explain the last result here? [1 2 3 Float/NaN] [1 2 3 NaN] (= Float/NaN Float/NaN) false This is a primitive comparison and follows IEEE floating point semantics. NaN must not equal NaN. ; all is good so far, but... (filter #(= % %) [1 2 3 Float/NaN 4]) (1 2 3 NaN 4) This is an Object comparison, and in Java this follows the contract for equals and hashCode. Thus, an object must be equal to itself (for HashMap to work). See: http://stackoverflow.com/questions/1408569/why-does-double-nan-equal-itself-when-wrapped-in-a-double-instance and in particular: http://docs.oracle.com/javase/6/docs/api/java/lang/Double.html#equals(java.lang.Object) Now I'm lost. What just happened? The behavior is strange, I've simplified it a bit to the following: ((fn [x] (= x x)) Float/NaN) true ((fn [x y] (= x y)) Float/NaN Float/NaN) false This is using Clojure 1.4.0 -- 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 -- 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
