As Jim already mentioned, you can use == to compare numbers for equality, but you must be cautious with equality for floating point numbers, as the tiniest bit of roundoff error will cause = and == to be false for such comparisons.
For =, there are effectively 3 'categories' of numeric values in Clojure, each of which can be = to each other within a category, but between categories values are never = to each other. Category 1. integer values (including Java Byte, Short, Integer, Long, BigInteger, and Clojure BigInt types) and ratio values (Clojure's Ratio type) Category 2. float and double values (Java Float and Double) Category 3. BigDecimal This is better than Java equals(), where Byte and Short are never equals() to each other, etc. Two numeric values must be the same Java class for equals() to be true. Why the 3 categories, you may wonder? I didn't design it myself, but my best guess is that in order to have a hash function (in this case Clojure's hash, implemented as a Java method called hasheq()) that is consistent with Clojure =, it is difficult to make such a hash function correct and fast if there were not these 3 separate categories. Andy On Mon, Jan 27, 2014 at 5:39 AM, Eric Le Goff <eleg...@gmail.com> wrote: > Newbie question : > > user=> (= 42 42) > true > user=> (= 42 42.0) > false > > I did not expect last result. > > I understand that underlying classes are not the same > i.e > user=> (class 42) > java.lang.Long > user=> (class 42.0) > java.lang.Double > > > but anyway I'am surprised > > Cheers > > > -- > Eric > > -- > -- > 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 unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
