#
#

calc <-
function()
{
 actionPerformed <- function(ev) {
   txt <- ev$getActionCommand()
   back <- 0
   if(txt == "=") {
     txt <- input$getText()
     val <- as.character(eval(parse(text=txt)))
     input$setText(val)
     jcombo$getModel()$insertElementAt(txt, as.integer(0))
     return(NULL)
   } else if(!is.na(match(txt, unaryOps))) {
     if(txt == "()")
       txt <- ""
     val <- paste(txt, "()",sep="")
     back <- -1
   } else if(txt == "Clear") {
      input$setText("")
      return(NULL)
   } else {
     val <- txt
   }
 
    doc <- input$getDocument()
    doc$insertString(input$getCaretPosition(), val, NULL)
    if(back < 0) {
      input$setCaretPosition(as.integer(input$getCaretPosition() + back))
    }
 }


 jdynamicCompile("java.awt.event.ActionListener", "RButtonListener")

 obj <- list(actionPerformed=actionPerformed)
 ref <- foreignReference(obj)
 l <- .JNew("RButtonListener", ref)

 numPad <- .JNew("JPanel")
 numPad$setLayout(.JNew("GridLayout", as.integer(4), as.integer(3), as.integer(5), as.integer(5)))
 for(i in c(1:9, 0, ".")) {
    b <- .JNew("JButton", i)
    b$addActionListener(l)
    numPad$add(b)
 }

 opPad <- .JNew("JPanel")
 unaryOps <- c("log", "exp", "sqrt", "()")
 opNames <- c("/", "*", "-", "+", unaryOps)
 opPad$setLayout(.JNew("GridLayout", as.integer(4), as.integer(2)))
 for(i in c("=", opNames, "Clear")) {
   b <- .JNew("JButton", i)
   b$addActionListener(l)
   opPad$add(b)
 }

 lowerPanel <-  .JNew("JPanel")
 lowerPanel$setLayout(.JNew("GridLayout", as.integer(1), as.integer(2)))
   lowerPanel$add("West",numPad)
   lowerPanel$add("East", opPad)


 topPanel <- .JNew("JPanel")
 topPanel$setLayout(.JNew("BorderLayout"))
 
# input <- .JNew("JTextField", as.integer(30))
 input <- .JNew("JComboBox")
 input$setEditable(T)

 go <- .JNew("JButton", "=")
 go$addActionListener(l)
 topPanel$add("East", go)
 topPanel$add("Center", input)

 panel <- .JNew("JPanel")
  panel$setLayout(.JNew("BorderLayout"))
 panel$add("North", topPanel)
 panel$add("Center", lowerPanel)


 f <- .JNew("GenericFrame", panel)


 jcombo <- input
 input <- input$getEditor()$getEditorComponent()

 list(ref, input=input)
}