I've been thinking of a practical way to `return` ...

# language-proposals

[David Rodrigues]

I've been thinking of a practical way to return a certain value based on a condition, and I'd like to propose this feature:

return x if != null
// <and/or>
return x if user != null

Same for break or continue
Other examples:

return x if >= 5
return x if is User
return x if x + 1 >= 5

And maybe:

x = 5 if x < 2

[jw]

Not sure if parenthesis are required to disambiguate some edge case, but regardless it's the same number of characters to do if (user != null) return x and it means you're aware of the conditional before seeing the action.

[David Rodrigues]

I don't know if it's a matter of my language (Portuguese), but it sounds better to me to say something like "return X if it is greater than 5" than "if X is greater than 5, return X itself". My suggestion was more towards code style and readability, but I don't know if it applies to everyone.

[Fleshgrinder]

It's correct English in both cases and both sound good. What does it return if the condition is not true? Null? Unit? This is basically where the current way shines, you have to have the else and there is nothing implicit.

return if (x is User) x else null

[hfhbd]

There was a similar request a few months ago, and I think the order is confusing.
At the moment, you read and execute from left to right, reading follows code execution, first condition, then its value/expression.

To understand the new syntax, you must read the condition first and then the value/expression. Reading does not follow the code execution. With complex expression, this is harder to understand, especially for a newcomer, I guess.

[Fleshgrinder]

Python has it all over and it's probably the most successful language among non programmers. If all of these people get it, well... 😉 The implicitness and the totally different syntax (no parentheses) are much more problematic in the context of Kotlin since this syntax has no precedence anywhere else and thus makes both the compiler and the language harder overall. This is actually true for Python. It is very inconsistent in how you have to write things at times.

[Klitos Kyriacou]

Richard Fussenegger:

What does it return if the condition is not true? Null? Unit?

I understood the OP as meaning that it doesn't return if it's not true. It carries on, same as if (x is User) return x without an else part.
I'm neither for nor against this proposition, but found it interesting as similar syntax appears in various other languages.