Is there a Scala Built-In Cache Class

There's nothing in the Standard Library built specifically for memory caching but it's easy enough to roll your own.

// memoize this function (arity 1) def memo1[A,R](f: A=>R): (A=>R) = new collection.mutable.WeakHashMap[A,R] { override def apply(a: A) = getOrElseUpdate(a,f(a)) } 

The reason for using WeakHashMap is that it is designed to drop (forget) seldom-accessed elements in a memory-challenged environment.

So this can be used to cache (memoize) existing methods/functions...

def s2l(s :String) :Long = ??? val s2lM = memo1(s2l) //memoize this String=>Long method val bigNum :Long = s2lM(inputString) //common inputs won't be recalculated 

...or you can define the function logic directly.

//memoized Long-to-Double calculation val l2dM = memo1{ n:Long => //Long=>Double code goes here } 

For functions with larger arity, use a tuple as the Map key.

def memo3[A,B,C,R](f :(A,B,C)=>R) :(A,B,C)=>R = { val cache = new collection.mutable.WeakHashMap[(A,B,C),R] (a:A,b:B,c:C) => cache.getOrElseUpdate((a,b,c), f(a,b,c)) }