scala lambda function and local variables

Question

As I am learning scal, I was wondering about optimisation when using local variables in lambda function.

For instance the following code :

val My_List = l.map{x =>
     val a = coomplexFun(x.attr_1, x.attr_2 ) ;
     (x.attr_1, doSomthing(a))
}

is it equivalent to :

val My_List = l.map{x =>
     (x.attr_1, doSomthing(coomplexFun(x.attr_1, x.attr_2 )))
}

Or is there some extra memory allocation cost?

Harald Gliebe · Accepted Answer · 2017-03-21 11:13:11Z

1

It is equivalent during runtime, since the JIT/Hotspot compiler will optimize it if necessary . The compiled class will be slightly larger since it contains information for the debugger, e.g. the name of the local variable.

answered Mar 21, 2017 at 11:13

Harald Gliebe

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2 Comments

Jörg W Mittag Over a year ago

Not all implementations of Scala have a JIT. Actually, no implementations of Scala have a JIT. Scala-native is a static AOT compiler that compiles to native machine code. Scala.js is a static AOT compiler that compiles to ECMAScript source code. That code may or may not then be executed on an execution engine with a JIT. Scala-JVM is a static AOT compiler that compiles to JVML bytecode. That bytecode may or may not then be executed on an execution engine with a JIT. E.g. the Excelsior JET JVM doesn't have a JIT. Or, you could further compile the JVM bytecode to Android bytecode, to be …

Jörg W Mittag Over a year ago

… executed by the ART, which doesn't have a JIT.

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