Any significant differences between lambda expressions & anonymous function in Kotlin?

Question

Kotlin has these 2 features and I think there're no significant differences between these two regardless of :

syntax

// lambda
val toUpper = { value: String -> 
   if (value.isEmpty()) "empty value"
   else value.toUpperCase()
}

// anonymous func
val toUpper = fun(value: String): String {
  if (value.isEmpty()) return "empty value"
  else return value.toUpperCase()
}

flexibility to use return statement on anonymous function

I'm still digesting these features and hope you guys can help me pass through it. Thanks.

It seems same to me, just like how A.() -> B is same as (A) -> B in bytecode (both are KFunction1<A, B>) but inside syntax is different A.() -> B lets you have this as receiver while (A) -> B lets you have variable of any name. Similarly (String) -> String can be assigned to both of them, i.e. fun one is also an implementation of KFunction1<String, String>. — Animesh Sahu
– Animesh Sahu, Commented Jul 2, 2020 at 5:25
See also: stackoverflow.com/questions/58004914/…, stackoverflow.com/questions/43166375/… — Alexey Romanov
– Alexey Romanov, Commented Jul 2, 2020 at 7:56
Does this answer your question? Kotlin fun() vs lambda is there difference? — Tenfour04
– Tenfour04, Commented Jul 2, 2020 at 14:00
@KelvinM did my answer resolve your question? If so please accept the answer :) — beastlyCoder
– beastlyCoder, Commented Jul 2, 2020 at 20:23

jingx · Accepted Answer · 2020-07-02 04:40:44Z

3

Two differences according to Kotlin Reference:

(I think the more significant one out of the two) An anonymous function is still a function, so returning from it behaves the same as returning from any function. Returning from a lambda, however, actually returns from the function enclosing the lambda.
The return type of a lambda is inferred, while you can explicitly specify a return type for an anonymous function.

answered Jul 2, 2020 at 4:40

jingx

4,0574 gold badges28 silver badges42 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Kelvin M Over a year ago

I think lambda's return type can be specified too, like val toUpper: (String) -> String { }

gidds Over a year ago

Kelvin M, that's not specifying the type of the lambda; it's specifying the type of variable you're assigning it to. In your example the effect is the same — but it's not if the lambda is used as a function parameter or in a more complex expression.

Raymond Arteaga · Accepted Answer · 2022-07-28 03:09:01Z

1

Besides the differences pointed by @jingx, you can not local return from a lambda that is not inlined.

So, the next snippet will not compile unless you add inline to the extension() function, thus, instructing the compiler to copy the function's content whenever it is referenced:

fun doSomethingWithLambda(){
    10.extension{
        if(it == 10)
            return//compiler error
    }
    println("hello")
}

fun Int.extension(f: (Int)->Unit){
    f(this)
}

answered Jul 28, 2022 at 3:09

Raymond Arteaga

4,6831 gold badge24 silver badges38 bronze badges

Collectives™ on Stack Overflow

Any significant differences between lambda expressions & anonymous function in Kotlin?

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related