Is there a better way of writing this without using scope functions, which I haven't introduced yet?

# codereview

[Ellen Spertus]

Is there a better way of writing this without using scope functions, which I haven't introduced yet?

Untitled.kt

[Luke]

How about:

fun readInt() : Int { 
    return generateSequence { readLine() }
        .mapNotNull { it?.toIntOrNull() }
        .first()
}

[ephemient]

.mapNotNull { ... }.first() == .firstNotNullOf { ... }

[ephemient]

but part of the loop seems like a bad idea. if readLine() returns null, that means you're at EOF and it will continue returning null

[ephemient]

if you use the readln() function, it'll instead throw an exception on EOF instead

[Klitos Kyriacou]

And in any case readLine() should be regarded as deprecated - if you still want its behaviour (instead of readln()), call readlnOrNull() which is a much more descriptive name.

[Ellen Spertus]

Thanks for all the feedback. Why should readLine() be regarded as deprecated? @Klitos Kyriacou

[Ellen Spertus]

I could be mistaken, but it doesn’t look like any of the alternatives re-prompt the user.

[Klitos Kyriacou]

readlnOrNull() does exactly the same thing as readLine() (so you can do a global search and replace) but has a more descriptive name.

[Klitos Kyriacou]

If you haven't introduced scope functions yet, then solutions using mapNotNull etc would presumably also be too advanced at this stage. I would keep your function definition as it is, but replace readLine()?.toIntOrNull() with readln().toIntOrNull().

[Klitos Kyriacou]

If you use readln() instead of readlnOrNull(), it will throw an exception if you enter ^D (or ^Z for those who use Windows), which is probably better than an infinite loop.

[ephemient]

exactly. instead of getting an infinite loop when null is returned from `readLine()`/`readlnOrNull()`, it would be much better to readln() and abort. that's what I was trying to hint at earlier