keys is lazy, you see the exception at the repl because printing out the result forces the sequence, but if you don't do anything with the result then it isn't forced, so no errors.
On 04/22/2016 01:28 PM, Steve Riley wrote: > I am trying to determine if a container, x, passed to a function, is a > map or not. > > If I evaluation (keys x) at a REPL prompt, and, x is instantiated list, > vector or set, I will get a java.lang.ClassCastException that some item > in x cannot be cast to java.util.Map$Entry. > > On the other hand, if I evaluate (try (keys x) true), the form evaluates > to true. It will also evaluation to true if I add a catch expression > with the last value of false. I've tried catching both > ClassCastException and just Exception. > > (try (/ 10 0) true (catch ArithmeticException _ "divide by zero!")) > and (try (/ 10 1) true (catch ArithmeticException _ "divide by zero!")), > for example, evaluate as expected. > > Is this a feature I don't understand? > > Some of you may recognize the 4Clojure problem I am working on. I'm not > interested in solutions to that problem...just curious about this > behavior and if there is something I am missing in the try (keys x) > catch formulation. > > Many thanks > > -- > 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 > <mailto:clojure+unsubscr...@googlegroups.com>. > For more options, visit https://groups.google.com/d/optout. -- And what is good, Phaedrus, And what is not good— Need we ask anyone to tell us these things? -- 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/d/optout.
