Hi all, do you know if message: String = "Hello $name" is lazy evaluated by default or not ? It's fo...

# getting-started

[vmichalak]

Hi all, do you know if message: String = "Hello $name" is lazy evaluated by default or not ? It's for optimisation purpose :)

[orangy]

@vmichalak what do you mean by lazy here?

[vmichalak]

The string concatenation between "Hello " and $name is made at the last moment or not ? (Sorry for my english 😣)

[noctarius]

It is done the second you do the assignment

[noctarius]

the string name might change afterwards, so it cannot be lazy and it cannot be done ahead of time, except name would be a constant

[orangy]

Type of message is String, so it has to do a full build to assign it.

[noctarius]

@orangy but I guess for a constant it’ll do compile time resolution? 🙂

[orangy]

No, it would be complicated and unpredictable, because it might need to call toString on name

[noctarius]

right, fair point 🙂

[orangy]

well, thinking about it a bit more (early morning, not yet even coffee), const types can only be primitives, String and may be classes, so may be it’s possible. But not sure it’s really needed. If performance is critical, you can always cache it yourself.

[noctarius]

I thought more about the “make a constant really constant”, not ending up in the same situation as Java with final 😉

[kirillrakhman]

@vmichalak if your usecase is logging or preconditions, you can use an inline lambda, like in require(person.age >= 18) { "$person must be over 18 years old." }

[kirillrakhman]

in this example, the string is only constructed, when the condition is false and an exception is thrown. otherwise the code is never executed.

[vmichalak]

Thanks a lot Kirill ! It's exactly what i search