CODEWITHSUNDEEP
scala
user2708013
user2708013

Reputation: 417

scala programming question about importing other objects

I am working on the examples of 99 scala problems.The question p11 i.e Modified run-length encoding. On the second line, it imports the object from p10 code "import P10.encode". My question here is when it gets into the below line of code 

encode(ls) map { t => if (t._1 == 1) t._2 else t }

I am aware that it maps P10 encode definition but how does it know from where it should get the t value? Does it work on the output such as if the output of p10 is List((1,1), (2,4), (1,3)) for the input encode(List(1,4,4,3)) or something else? Please enlighten me

Upvotes: 0

Views: 58

Answers (1)

Dominic Egger
Dominic Egger

Reputation: 1016

so the t is just an identifier for an anonymous function parameter.

I am assuming that encode(ls) returns List[(Int, Int)] so that means that map has the following signature map[B](f : ((Int, Int)) => B)

this means it requires a function from Int (which is what's in the list) to some other type.

t => if (t._1 == 1) t._2 else t is a literal for a function that takes one parameter called t (the compiler can infere that it has to be an (Int, Int) due to the literal being in the parameter position of map on a List[(Int, Int)]) and and returns a single Int yielding a List[Int] after the map

really it could also have been x => if (x._1 == 1) x._2 else x it's just a local name

EDIT: Added parens for the int tuple in map as per comment. woops

Upvotes: 2

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