Avoiding boxing/unboxing within function

Question

For a numeric intensive code I have written a function with the following signature:

def update( f: (Int,Int,Double) => Double ): Unit = {...}

Answer 1

About the anonymous class which extends Function3 (the bytecode of which you show) generated by Scalac - it is not possible to call the overloaded apply with primitive parameters from within the b.update, because that update method takes a Function3, which does not have an apply with primitive parameters.

From within the Function3 bytecode, the only apply is:

public abstract java.lang.Object apply(java.lang.Object, java.lang.Object, java.lang.Object);

You could instead use Function2[Long, Double], which is specialized on those types, and encode 2 integers x and y in a long as (x.toLong << 32) + y, and decode them as v & 0xffffffff and (v >> 32) & 0xffffffff.