这是我的第一个程序:
为什么会抛出异常?
(println "hello, what is your name?")
(let [myname (read-line)]
((println (str "hello " myname))))
有点儿可行:
hello, what is your name?
Joel
hello Joel
Exception in thread "main" java.lang.NullPointerException, compiling:(/home/joel/workspace/coolstuff/clojure/hello.clj:1:38)
at clojure.lang.Compiler.load(Compiler.java:7142)
at clojure.lang.Compiler.loadFile(Compiler.java:7086)
at clojure.main$load_script.invoke(main.clj:274)
at clojure.main$script_opt.invoke(main.clj:336)
at clojure.main$main.doInvoke(main.clj:420)
at clojure.lang.RestFn.invoke(RestFn.java:408)
at clojure.lang.Var.invoke(Var.java:379)
at clojure.lang.AFn.applyToHelper(AFn.java:154)
at clojure.lang.Var.applyTo(Var.java:700)
at clojure.main.main(main.java:37)
Caused by: java.lang.NullPointerException
at user$eval3.invoke(hello.clj:3)
at clojure.lang.Compiler.eval(Compiler.java:6703)
at clojure.lang.Compiler.load(Compiler.java:7130)
... 9 more
为什么会抛出异常?