Exactly when I tough i was getting pro at kotlin I...

# getting-started

[Daniele Segato]

Exactly when I tough i was getting pro at kotlin I fall on the most basic thing...

this code below do not compile 🙂

I know about ranges...
I can do in Int.MIN_VALUE until 0

I also know I can save the value and compare to 0 using a when with no parameter.

But are these really the only ways? Can't I do something similar to the code below?

And to check !0 with ranges I would have to write:
!in in 1..Int.MAX_VALUE && !in -1 downTo Int.MIN_VALUE

But this doesn't look right, there must be another way, right?

open_integer_conditions_in_when.m

[Andreas Sinz]

Only in, is or a comparison == with an expression is supported by when right now

[Daniele Segato]

😞
so what I wrote is actually the only way

except -1 downTo Int.MIN_VALUE is converted into 2 comparison while x < 0 would be only 1

[Shawn]

why not just

[Shawn]

have an if/else here

[Andreas Sinz]

or use when differently:

val x = functionReturningInteger()
when {
    x < 0 -> { }
    x > 0 -> { }
   ...
}

[Daniele Segato]

yes, I did that too..

slightly differently

functionReturningInteger().let{ when { .... } }

[Daniele Segato]

i almost never use val = ... in my code, I usually prefer using let, apply, with and so on...

not sure if that's a good idea

[Shawn]

if you do so at the expense of your code’s readability, then it’s a terrible idea

[Shawn]

there’s nothing wrong with assigning some variables here and there if it makes the relevant block easier to comprehend

[Shawn]

the problem is unnecessary noise, not assignments at large

[Daniele Segato]

I don't know, i like this more:

return day.compareTo(other.day).let { if (it != 0) it else time.compareTo(time) }

then this:

val comparison = day.compareTo(other.day)
return if (comparison != 0) comparison else time.compareTo(time)

is it just me?

[Shawn]

in that case I’d say that repeating comparison over and over isn’t making it easier to read

[Shawn]

it’s not an indictment of val x = ... as a whole

[Shawn]

just an example of where it doesn’t make things clearer

[Shawn]

maybe something like this would read a bit more naturally

[Shawn]

return day.compareTo(other.day)
        .takeIf { it != 0 }
        ?: time.compareTo(other.time)

[Alowaniak]

Well in that particular case you should be able to do something like compareBy({it.day},{it.time}).compare(this,other) afaict

Or compareValuesBy or w/e

[Daniele Segato]

Ah!! takeIf i didn't know about... Is there a list of all of this? Thanks by the way.

Also didn't know about compareBy!

[Daniele Segato]

I knew let, use, apply, also and with :-) but couldn't find a list with all