## Example of string class using OOP
## similar to string class in ruby
require(OOP)

defineClass("String")
String$defineFields(string = "character")

## New.
String$defineMethod("initialize",
                    function(val) {
                      set.string(as.character(val))
                    })
## simpler interface
string = function(x) String$new(x)

## length
String$defineMethod("length",function() {
  return(nchar(string))
})
## summary
String$defineMethod("summary",function() {
  return(table(strsplit(string,""))) 
})

## show . show() is for S4 methods, These are not. Still
## need a print method defined below
String$defineMethod("show", function() cat(string,"\n"))

## slice
String$defineMethod("slice",function(index) {
  splitUpString = unlist(strsplit(string,""))
  tmp = splitUpString[index]
  return(String$new(paste(tmp,sep="",collapse="")))
})

### Concatanation
String$defineMethod("concat",function(y,sep="") {
  return(String$new(paste(string,as.character(y),sep=sep)))
})

## repeat
String$defineMethod("rept",function(n,sep="") {
  return(String$new(paste(rep(string,n),sep=sep,collapse="")))
})


## split on a regexp
## returns a vector of characters!
String$defineMethod("split",function(by="") {
  unlist(strsplit(string,by))
})

## modify the value in place
String$defineMethod("upcase",function() {
  set.string(toupper(string))
})

## return upcased value as string object
String$defineMethod("upcase.it",function() {
  String$new(toupper(string))
})

String$defineMethod("downcase",function() {
  String$new(tolower(string))
})

## S4 Methods for syntactical sugar
setMethod("print","String", function(x,...) x$show())
setMethod("[","String",function(x,i,j,...,drop) x$slice(i))
setMethod("+","String",function(e1,e2) e1$concat(e2))
setMethod("*","String",function(e1,e2) e1$rept(e2))
setMethod("/","String",function(e1,e2) e1$split(e2))

### S3 style methods would look like this
### print.String = function(self) self$show()
### "[.String" = function(self,index) self$slice(index)
### "+.String" = function(self,x) self$concat(x)
### "*.String" = function(self,n) self$rept(n)
### "/.String" = function(self,y) self$split(y)


defineClass("Sentence", extends = "String")
Sentence$defineMethod("punctuate",function() {
  ## add a period, and capitalize the first letter
  chars = split("")
  chars[1] = toupper(chars[1])
  if(chars[(length)(chars)] != ".")
    chars[(length)(chars)+1] = "."

  set.string(paste(chars,sep="",collapse=""))

})