How Does One Make Scala Control Abstraction in Repeat Until?
- by peter_pilgrim
Hi
I am Peter Pilgrim. I watched Martin Odersky create a control abstraction in Scala. However I can not yet seem to repeat it inside IntelliJ IDEA 9. Is it the IDE?
package demo
class Control {
def repeatLoop ( body: = Unit ) = new Until( body )
class Until( body: = Unit ) {
def until( cond: = Boolean ) {
body;
val value: Boolean = cond;
println("value="+value)
if ( value ) repeatLoop(body).until(cond)
// if (cond) until(cond)
}
}
def doTest2(): Unit = {
var y: Int = 1
println("testing ... repeatUntil() control structure")
repeatLoop {
println("found y="+y)
y = y + 1
}
{ until ( y < 10 ) }
}
}
The error message reads:
Information:Compilation completed with 1 error and 0 warnings
Information:1 error
Information:0 warnings
C:\Users\Peter\IdeaProjects\HelloWord\src\demo\Control.scala
Error:Error:line (57)error: Control.this.repeatLoop({
scala.this.Predef.println("found y=".+(y));
y = y.+(1)
}) of type Control.this.Until does not take parameters
repeatLoop {
In the curried function the body can be thought to return an expression (the value of y+1) however the declaration body parameter of repeatUntil clearly says this can be ignored or not?
What does the error mean?
