Hi! > I tried this: (var (symbol name)) > but that caused the exception: clojure.lang.PersistentList cannot be > cast to clojure.lang.Symbol
var is a special form. If var was a function, (symbol name) would have been evaluated and the result would have been passed to var as an argument. Special Forms and macros don't necessarily work that way - it's up to them to decide how to treat the arguments. You can use ns-resolve to find a var by name: user=> (def x 1) #'user/x ; find the var. *ns* is bound to the current namespace user=> (ns-resolve *ns* (symbol "x")) #'user/x ; get the value user=> (deref (ns-resolve *ns* (symbol "x"))) 1 :shorter way of deref'ing user=> @(ns-resolve *ns* (symbol "x")) 1 clojure.core/ns-resolve ([ns sym]) Returns the var or Class to which a symbol will be resolved in the namespace, else nil. Note that if the symbol is fully qualified, the var/Class to which it resolves need not be present in the namespace. Hope this helps. Kind regards, achim Am 06.03.2009 um 15:23 schrieb timc: > > I would like to have a function which tells me about the values of a > var, where the parameter to the function is a string equal to the > 'name' of the var. > > For example: > > (defn checkNil [name] > "If the var with the given (String) name is nil, display a > message; result = value of var". > (when (nil? (value of the var called name)) > (display (str name " is nil"))) > (value of the var called name)) > > so that > > (def x nil) > (checkNil "x") > > should display: "x is nil" -- (display s) being a function that shows > the string s somewhere. > > The question is, how do I express (value of the var called name)? > > I tried this: (var (symbol name)) > but that caused the exception: clojure.lang.PersistentList cannot be > cast to clojure.lang.Symbol > > Is this possible? > > ---------------- > Another way to do it would be as follows. > > (defn checkNil [x] > "If the variable x is nil, display a message; result = value of > x." > (when (nil? x) > (display (str (name of the var x) ) " is nil"))) > x) > > so that > > (def x nil) > (checkNil x) > > should display: "x is nil". > > In this case - how to do: (name of the var x)? > > --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
