Making a function with val can be shorter than with a def

If you're pattern matching, you can use Scala's special syntax and omit match when assigning an anonymous function to a val. As you can see, it's a lot shorter:

val g:List[Int]=>Int={case h::t=>h+g(t)case _=>0}
def f(l:List[Int]):Int=l match{case h::t=>h+f(t)case _=>0}

You can also use underscore syntax. For certain functions, this is always profitable. For others, like the example below, where the type of the parameter cannot be inferred, it is only profitable when you have only one parameter with a type ascription.

val g=(_:Int)+1
def f(i:Int)=i+1

However, if you need to reuse a function, make a def instead of a val. Consider these two pairs of functions:

//Recursive
def f(i:Int):Int=if(i>0)i*f(i-1)else 1
val f:Int=>Int=i=>if(i>0)i*f(i-1)else 1

//Non-recursive functions are also shorter with def
def f(i:Int)=i+1
val g=(i:Int)=>i+1

posted over 3 years ago

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