Scala companion object with abstract class -

i'm reading book programming in scala (second edition) martin odersky , have problem examples in chapter 10.

this file @ end of chapter:

class element object element {    private class arrayelement(     val contents: array[string]   ) extends element    private class lineelement(s: string) extends arrayelement(array(s)) {     override def width = s.length     override def height = 1   }    private class uniformelement(     ch: char,     override val width: int,     override val height: int   ) extends element {     private val line = ch.tostring * width     def contents = array.fill(height)(line)   }    def elem(contents: array[string]): element =     new arrayelement(contents)    def elem(chr: char, width: int, height: int): element =     new uniformelement(chr, width, height)    def elem(line: string): element =      new lineelement(line)  }  abstract class element {   def contents: array[string]    def width: int =      if (height == 0) 0 else contents(0).length    def height: int = contents.length    def above(that: element): element =     elem(this.contents ++ that.contents)    def beside(that: element): element =     elem(       (         (line1, line2) <- this.contents zip that.contents       ) yield line1 + line2     ) } 

the compiler says this:

defined class element <console>:15: error: method width overrides nothing            override def width = s.length                         ^ <console>:16: error: method height overrides nothing            override def height = 1                         ^ <console>:21: error: value width overrides nothing            override val width: int,                         ^ <console>:22: error: value height overrides nothing            override val height: int                         ^ <console>:17: error: not found: value elem            elem(this.contents ++ that.contents)            ^ <console>:20: error: not found: value elem            elem(            ^ 

if remove class element beginning complains element type not found when try subclass it.

i found couple topics here discussing chapter book couldn't use of proposed solutions there.

what did miss?

regards, norbert

first, declare class element twice - remove first line, confusing things (this doesn't cause errors me - if you, can show more info on error?). should fix override errors. second, method elem companion object isn't automatically visible in class. either prefix element wherever used or - better - add import line @ start of class:

object element {   ... }  abstract class element {   import element._   ... } 

edit: ah, might have idea why error when leave off first line. if trying in repl , entering 1 line (or 1 declaration) @ time, might hit issue because repl doesn't forward referencing required. try pasting code in @ once (using ":paste" in repl).