scala/scala

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Emily Pillmore

@emilypi

I’ll leave that up to you

celik sismanturk

@celik0311

:+1:

i would pattern that the next item isnt Nil correct?

Emily Pillmore

@emilypi

yes. But make sure the function is total. You’ll need 3 cases to do this

Rob Norris

@tpolecat

gitter seems to be freaking out

not that there's anything wrong with that

David Dudson

@DavidDudson

is there a nice way to span from the end of a string???

I cant see it other then implementing it myself. Reversing strings seems innefficient

Ghost

@ghost~54f4b69115522ed4b3dcb16d

@DavidDudson s.lastIndexWhere(!p)is where to split.

Rob Norris

@tpolecat

mind the -1

David Dudson

@DavidDudson

I guess math.min(s.lastIndexWhere(!p) + 1, s.length) would work

It's interesting that takeRightWhile is missing too. I must have a nosy at these new collections

celik sismanturk

@celik0311

i am having trouble understanding where to add the case statements in that fold statement

Rob Norris

@tpolecat

I would just write out the recursive method and then maybe rewrite it with foldRight. The important thing is to understand what’s going on.

celik sismanturk

@celik0311

my understanding is that acc is the new list and we are just cocating to it as we get each element

i would guess i would that i would patten match on elem but how would i know its the last item?

case x::Nil?

David Dudson

@DavidDudson

Given a list roughly like....

B :: A :: C :: B :: C :: Nil

Is there a functional way of finding the first B after an A, without multiple traversals?

Rob Norris

@tpolecat

list.dropWhile(_ != A).find(_ == B)

One traversal, no allocation other than the Some(x) if the value is found.

David Dudson

@DavidDudson

@tpolecat I like it! thanks. It works perfectly with Cons lists

Rob Norris

@tpolecat

Cons lists are the best.

David Dudson

@DavidDudson

sharing memory is great

celik sismanturk

@celik0311

i think i figured out a solution is there a dowside to generating the list above and the calling .init basically just remove the last element aka the newline

lines.foldLeft(Nil:List[Char])((acc, cs)=> acc ::: (cs :+ '\n')).init

seemed consise which is why I choose it but again scala is pretty new to me so maybe im overlooking something

Dhiraj himani

@dk_hemani_twitter

I am not able to understand this behaviour
val l1 = mutable.LinkedList(1,2,3,4,5)
l1.next = l1
and after this the l1 becomes empty
println(l1)
gives output:
{}

Dhiraj himani

@dk_hemani_twitter

        val l1 = scala.collection.mutable.LinkedList(1,2,3,4,5)
        l1.next = l1
        println(l1)

output: LinkedList()

Ghost

@ghost~55118a7f15522ed4b3ddbe95

https://github.com/scala/scala/blob/2.13.x/src/library/scala/collection/mutable/LinkedListLike.scala#L64

I am pretty sure this is the reason why

last element of a linked list points to itself

Dhiraj himani

@dk_hemani_twitter

Thanks

Dhiraj himani

@dk_hemani_twitter

It took my much time

Thanks for helping out

Ghost

@ghost~55118a7f15522ed4b3ddbe95

np ;)

Ghost

@ghost~540393fe163965c9bc2018ce

@celik0311 what you're writing looks an awful lot like lines.intercalate("\n") from scalaz

I think the stdlib also gives you .mkString, which is less principled and only works for this one usecase.

Rich

@Rich2

When passing parameters to a super class is there anything wrong with putting a multiline code block in the superclass constructor?

Subclass(a: A, b: B) extends SuperClass({ stuff; stuff; result}, other parameters)

Jose C

@jmcardon

Aside from it being a little odd, I Don't think so

Martijn Hoekstra

@martijnhoekstra

it looks really dodgy to me, but I can't formulate why, so feel free to ignore my dodgy feelings

Jose C

@jmcardon

I don't know why you'd do a calculation to pass a parameter though

It seems like a really strange thing to do

but I've actually never even seen anyone do that so I can't even call it an anti-pattern

Rich

@Rich2

I've got regular rectangular grids that have a min and max x and y coordinates. But I've also got irregular grids that have an Array that gives the min and max x for each row. The calculation is to get the overall min and max x for the irregular grid from the Array.

Rich

@Rich2

Have constructors for non-case classes become unfashionable?

Jose C

@jmcardon

it's not that, just rather that making a calculation inside the constructor paramter is not common in scala, I guess

Rich

@Rich2

No well I can't say I have seen it in other languages either. I guess the syntax is not possible in most languages.

Martijn Hoekstra

@martijnhoekstra

In the scala I write I don't think I've ever inhereied from a superclass with a constructor - but that might say more about me than about scala or whether or not that's a good idea.

Rich

@Rich2

I think not having constructors in traits, I suspect has got Scala developers into the habit of not using them.

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