## project.clj

(defproject calculator "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "Eclipse Public License"
            :url "http://www.eclipse.org/legal/epl-v10.html"}
  :dependencies [[org.clojure/clojure "1.5.1"]
		[seesaw "1.4.4"]])

## src/calculator/core.clj

 1(ns calculator.core
 2        (:require [seesaw.core :refer :all]))
 3
 4(native!)
 5
 6(def main-frame (frame :title "Calculator" :on-close :exit))
 7
 8(def field-x (text "1"))
 9(def field-y (text "2"))
10
11(def result-label (label "Type numbers in the boxes to add them up!"))
12
13(defn update-sum [e]
14     (try
15       (text! result-label
16            (str "Sum is " (+ (Integer/parseInt (text field-x))
17                (Integer/parseInt (text field-y)))))
18       (catch Exception e
19         (println "Error parsing input."))))
20
21(listen field-x :key-released update-sum)
22(listen field-y :key-released update-sum)
23
24(config! main-frame :content
25            (border-panel
26             :north (horizontal-panel :items [field-x field-y])
27             :center result-label
28             :border 5))
29
30(defn -main [& args]
31    (-> main-frame pack! show!))
32

## $ lein run -m calculator.core...

Exception in thread "main" java.lang.RuntimeException: Unable to resolve symbol:  in this context, compiling:(calculator/core.clj:16:28)
	at clojure.lang.Compiler.analyze(Compiler.java:6380)
	at clojure.lang.Compiler.analyze(Compiler.java:6322)
	at clojure.lang.Compiler$HostExpr$Parser.parse(Compiler.java:948)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6560)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.analyze(Compiler.java:6322)
	at clojure.lang.Compiler$HostExpr$Parser.parse(Compiler.java:948)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6560)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.analyze(Compiler.java:6322)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6555)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.analyze(Compiler.java:6322)
	at clojure.lang.Compiler$InvokeExpr.parse(Compiler.java:3624)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6562)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.analyze(Compiler.java:6322)
	at clojure.lang.Compiler$InvokeExpr.parse(Compiler.java:3624)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6562)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.analyze(Compiler.java:6322)
	at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5708)
	at clojure.lang.Compiler$TryExpr$Parser.parse(Compiler.java:2156)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6560)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.analyze(Compiler.java:6322)
	at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5708)
	at clojure.lang.Compiler$FnMethod.parse(Compiler.java:5139)
	at clojure.lang.Compiler$FnExpr.parse(Compiler.java:3751)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6558)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6548)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.access$100(Compiler.java:37)
	at clojure.lang.Compiler$DefExpr$Parser.parse(Compiler.java:529)
	at clojure.lang.Compiler.analyzeSeq(Compiler.java:6560)
	at clojure.lang.Compiler.analyze(Compiler.java:6361)
	at clojure.lang.Compiler.analyze(Compiler.java:6322)
	at clojure.lang.Compiler.eval(Compiler.java:6623)
	at clojure.lang.Compiler.load(Compiler.java:7064)
	at clojure.lang.RT.loadResourceScript(RT.java:370)
	at clojure.lang.RT.loadResourceScript(RT.java:361)
	at clojure.lang.RT.load(RT.java:440)
	at clojure.lang.RT.load(RT.java:411)
	at clojure.core$load$fn__5018.invoke(core.clj:5530)
	at clojure.core$load.doInvoke(core.clj:5529)
	at clojure.lang.RestFn.invoke(RestFn.java:408)
	at clojure.core$load_one.invoke(core.clj:5336)
	at clojure.core$load_lib$fn__4967.invoke(core.clj:5375)
	at clojure.core$load_lib.doInvoke(core.clj:5374)
	at clojure.lang.RestFn.applyTo(RestFn.java:142)
	at clojure.core$apply.invoke(core.clj:619)
	at clojure.core$load_libs.doInvoke(core.clj:5413)
	at clojure.lang.RestFn.applyTo(RestFn.java:137)
	at clojure.core$apply.invoke(core.clj:619)
	at clojure.core$require.doInvoke(core.clj:5496)
	at clojure.lang.RestFn.invoke(RestFn.java:408)
	at user$eval5$fn__7.invoke(form-init425199259213285636.clj:1)
	at user$eval5.invoke(form-init425199259213285636.clj:1)
	at clojure.lang.Compiler.eval(Compiler.java:6619)
	at clojure.lang.Compiler.eval(Compiler.java:6609)
	at clojure.lang.Compiler.load(Compiler.java:7064)
	at clojure.lang.Compiler.loadFile(Compiler.java:7020)
	at clojure.main$load_script.invoke(main.clj:294)
	at clojure.main$init_opt.invoke(main.clj:299)
	at clojure.main$initialize.invoke(main.clj:327)
	at clojure.main$null_opt.invoke(main.clj:362)
	at clojure.main$main.doInvoke(main.clj:440)
	at clojure.lang.RestFn.invoke(RestFn.java:421)
	at clojure.lang.Var.invoke(Var.java:419)
	at clojure.lang.AFn.applyToHelper(AFn.java:163)
	at clojure.lang.Var.applyTo(Var.java:532)
	at clojure.main.main(main.java:37)
Caused by: java.lang.RuntimeException: Unable to resolve symbol:  in this context
	at clojure.lang.Util.runtimeException(Util.java:219)
	at clojure.lang.Compiler.resolveIn(Compiler.java:6874)
	at clojure.lang.Compiler.resolve(Compiler.java:6818)
	at clojure.lang.Compiler.analyzeSymbol(Compiler.java:6779)
	at clojure.lang.Compiler.analyze(Compiler.java:6343)
	... 72 more