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Posted By

narkisr on 08/11/09


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closure groovy functional memoization


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Closure memoization in Groovy

 / Published in: Groovy
 

URL: http://cromwellian.blogspot.com/2006/07/infinite-streams-in-groovy-in-my-last.html

This example shows how its possible to cache (memoization) a Closure value, note that this works only for a single value per each delay method call (the Closure creates a closed scope in which its "state" is kept).

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  1. public delay(Closure c)
  2. {
  3.    boolean evaled=false
  4.    def val=null
  5.    return {Object[] args -> 
  6.                if(!evaled) { evaled=true; val=c(args[0]); return val } 
  7.                else return val;
  8.    }
  9. }
  10.  
  11. c = {v ->
  12.  println 'hello'
  13.  1+v
  14.  
  15. }
  16.  
  17. d = delay(c)
  18. println d.call(1)
  19. println d.call(1)// hello will not be printed
  20. println d.call(2)// we will not eval, the result will be 2 & not 3!

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